scholarly journals V.—On the Denticulated Structure of the Hinge–line of Spirifera trigonalis, Martin

1884 ◽  
Vol 1 (1) ◽  
pp. 18-20 ◽  
Author(s):  
John Young
Keyword(s):  
Outer Edge ◽  
Ventral Valve ◽  
Dorsal Valve ◽  
Hinge Line ◽  
Lower Carboniferous ◽  
Fossiliferous Limestone ◽  
The Way

Recently, when examining some weathered fossiliferous limestone shale from the Lower Carboniferous strata of East Kilbride, Lanarkshire, my attention was attracted to some fragments of the valves of Spirifera trigonalis, Martin, in which I noticed, on the hinge-line of the dorsal valve, a row of small, round, hollow pits, and on the hinge-line of the ventral valve, a corresponding row of small, projecting, rounded denticles. These characters I had not noticed before, and on searching further, I found other fragments of the valves showing the same thing. This led to an examination of more perfect specimens of this Spirifera, contained in my own collection, and that of Dr. J. R. S. Hunter, of Braidwood, Carluke, and in one example, where the valves had slightly opened through pressure, on clearing away the shale, I found, on the outer edge of the ventral valve, a distinct row of small projecting denticles, that had evidently fitted into hollow pits or sockets in the dorsal valve, but from the way the valves had shifted in this specimen these were not seen. These denticles, when looked at externally, are nearly as numerous, and much of the same size, as those seen in many of the hinge-lines of shells of the genus Area, only in this genus, the teeth are the same in each valve, and lock into each other.

The Carboniferous System in Scotland Characterized by its Brachiopoda

The Geologist ◽  
1860 ◽  
Vol 3 (1) ◽  
pp. 14-25
Author(s):  
Thomas Davidson
Keyword(s):  
Great Difficulty ◽  
Ventral Valve ◽  
Dorsal Valve ◽  
Hinge Line ◽  
The Subject ◽  
Spiral Coils ◽  
Extinct Genus ◽  
External Shape

The shells of which this genus is composed differ much in their external shape and appearance, hence the great difficulty of correctly determining the limits of certain species. The character of this extinct genus are now so well understood that it is scarcely necessary to make any further allusion to the subject; but we may briefly repeat, for the sake of the less initiated, and in order to shorten the descriptions of the various species, that all possess a straight hinge-line, and a triangular or sub-parallel area, which is divided by a triangular fissure, this last being more or less covered, or contracted, by the means of one or two curved plates, to which the term pseudo-deltidium has been applied. The pseudo-deltidium is rarely preserved in the carboniferous specimens, but did certainly exist in the perfect or living individuals. The valves are articulated by the means of curved teeth developed on either side of the fissure in the ventral valve, and which fit into corresponding sockets in the opposite or dorsal one. In the larger valve the teeth are supported by vertical plates of greater or lesser dimensions, and in the space between these on the bottom of the shell are situated the muscular impressions. The adductor, or occlusor muscle leaves a narrow mesial oval-shaped scar, and on either side are situated the cardinal, or divaricator muscular impressions. In the interior of the smaller, or dorsal valve there exists two large conical spiral coils, which nearly fill the interior of the shell, the ends being directed outwardly towards the cardinal angles, while the bases of the hollow conical spires nearly meet at the hinge side, but are wide apart in front.

The Carboniferous System in Scotland Characterized by its Brachiopoda

The Geologist ◽  
1860 ◽  
Vol 3 (6) ◽  
pp. 219-240
Author(s):  
Thomas Davidson
Keyword(s):  
Ventral Valve ◽  
Dorsal Valve ◽  
Entire Surface ◽  
Hinge Line ◽  
Cardinal Process

The shells composing this species vary but slightly in shape, being marginally semicircular, concavo-convex, and about one-third wider than long. The hingeline is straight, and either a little shorter, with its cardinal angles rounded, or somewhat longer than the greatest width of the shell, with rectangular or slightly acute and extended terminations. Both valves are provided with narrow sub-parallel areas, the ventral one, which is the largest, being divided by a small fissure, partially covered with a pseudo-deltidium; while in the middle of the ventral one there exists a prominent V-shaped cardinal process. The ventral valve is moderately convex, and flattened towards its auriculate cardinal extremities. The beak, which is small and incurved, does not overlie the hinge-line; while the dorsal valve assumes in different specimens a greater or lesser degree of concavity, and follows the curves of the opposite one. Exteriorly the surface of the ventral valve is covered with numerous small thread-like radiating striæ, which increase in number by occasional bifurcation, or interstriations at various distances from the beak, so that as many as one hundred and twenty ribs may be counted round the margin of certain specimens, while at irregular distances small spines projected from the rounded surface of the striæ. In addition to these, on each side of the beak there exists along the cardinal edge from five to nine slanting tabular spines, which become longer and larger as they approach the extremities of the cardinal edge. The surface of the dorsal valve is striated as in the ventral one; and minute perforations or punctures may be perceived over the entire surface of the shell, and which are the exterior orifices of the canals which traverse the shell, as in Productus.

New Lower Ordovician Brachiopods from the Llandeilo-Llangadock District

1949 ◽  
Vol 86 (4) ◽  
pp. 226-238 ◽  
Author(s):  
Alwyn Williams
Keyword(s):  
Ventral Valve ◽  
Dorsal Valve ◽  
Hinge Line ◽  
Lower Ordovician

External characters.—Plano-convex with a moderately deep ventral valve and a plane to slightly convex dorsal valve. Outline is semi-oval with the greatest width just anterior to the long straight hinge-line. Ventral interarea, wide, long, apsacline, dorsal interarea, anacline.

VII.—On a New Genus and Species of the Thecidinæ (Brachiopoda)

1915 ◽  
Vol 2 (10) ◽  
pp. 461-464 ◽  
Author(s):  
J. Allan Thomson
Keyword(s):  
Anterior Margin ◽  
New Genus ◽  
Ventral Valve ◽  
Dorsal Valve ◽  
New Genus And Species ◽  
Hinge Line ◽  
Cardinal Process ◽  
The Family ◽  
Anterior Septum

The subfamilies Thecidiinæ, Dall, and Leptodinæ, Schuchert, constitute the family Thecidiidæ, Gray, which is regarded by Schuchert as a near relation of the Strophomenidæ. The chief external characters of the Thecidiinæ are the smallness of the shells, the absence of the foramen, attachment by the ventral valve, the presence of a nearly straight hinge-line and of a prominent area with a solid deltidium. The shell substance, with the exception of the deltidium, is punctate. Internally the ventral valve bears in its hollow beak a small edian septum on which is sometimes superposed a small muscular plate. The dorsal valve bears a so-called cardinal process, formed by the median union of the socket ridges, and this plate is strong, subrectangular, and hollow at its base, and projects beyond the hinge. In most of the genera two lateral spurs unite mesially to form a bridge just in front of the cardinal process, over the visceral cavity. There are no free brachial arms, but the brachial supports are represented by an anterior septum, frequently branched, and lamellae rising from the floor of the valve in the spaces between the septum and its branches, the margins, and the bridge. The septum runs back from the anterior margin towards the bridge, and like the margins and the bridge, is more or less covered with granulations.

VII.—On a New form of Spiral in Spirifera glabra

1890 ◽  
Vol 7 (10) ◽  
pp. 461-463
Author(s):  
Norman Glass
Keyword(s):  
Ventral Valve ◽  
Dorsal Valve ◽  
Shell Surface ◽  
Hinge Line ◽  
Lateral Margins ◽  
New Form

In Davidson's Monograph of the British Carboniferous Brachiopoda (1857), p. 60, he gives the following specific characters of Spirifera glabra:—“Very variable in shape and proportions; transversely oval, rarely as long or longer than wide. Valves almost equally convex, with a mesial elevation or fold in the dorsal, and a sinus in the ventral valve. Hinge-line much shorter than the greatest width of the shell; cardinal angles rounded; beaks rather approximate, that of the larger or ventral valve prominent, incurved, and of moderate dimensions. A hinge-area in the dorsal valve, that of the ventral one triangular and of moderate dimensions, with its lateral margins more or less sharply defined; fissure partially covered by a pseudo-deltidium. The mesial fold in the dorsal valve is either slightly and evenly convex, rising gradually from the lateral portions of the valve, or abruptly elevated, with a longitudinal depression along its middle, which is also at times reproduced in the sinus of the ventral one. The spiral appendages are large, and occupy the greater portion of the interior of the shell. Surface of valves in general smooth, but sometimes a few obscure rounded ribs may be observed on their lateral portions”

V.—Woodwardian Museum Notes

1898 ◽  
Vol 5 (6) ◽  
pp. 266-267
Author(s):  
F. R. Cowper Reed
Keyword(s):  
Careful Examination ◽  
Ventral Valve ◽  
Dorsal Valve ◽  
Hinge Line ◽  
Margin Entire ◽  
Anterior Edge

In rearranging the Carboniferous fossils in the Woodwardian Museum, I met with a specimen labelled Aihyris, n.sp., which reminded me of the form described by De Koninck as Terebratula serpentina. On careful examination I am convinced that it belongs to this species, and the following is a description of our specimen:— Shell subovate, terebratuliform, widest at about one-third its length from its anterior edge. Valves moderately convex, slightly flattened anteriorly, and devoid of sinus and fold; margin entire and regular. Ventral valve a little less deep than dorsal valve, and furnished with a slightly recurved beak truncated by a large circular foramen, bordered in front by a pair of deltidial plates. Surface of both valves ornamented with straight, radiating, very faint ribs, 60 to 70 in number, arranged in a regular close series separated by weak narrow furrows. Some of the ribs bifurcate at about half their length, and those near the hinge-line curve gently backwards. Shell substance finely punctate. Concentric strife of growth are distinct on both valves. Length, 25 mm.; breadth, 22 mm.; dorsiventral diameter, 12 mm.

scholarly journals Schizocrania (Brachiopoda, Discinoidea): taxonomy, occurrence, ecology and history of the earliest epizoan lingulate brachiopod

2016 ◽  
Vol 72 (3-4) ◽  
pp. 225-238 ◽  
Author(s):  
Michal Mergl ◽  
Lucie Nolčová
Keyword(s):  
Trophic Structure ◽  
Ventral Valve ◽  
Dorsal Valve ◽  
Early Devonian ◽  
Sea Floor ◽  
Open Sea ◽  
History Of ◽  
Barrandian Area ◽  
Floating Objects ◽  
First Time

The lingulate brachiopod Schizocrania (Trematidae, Discinoidea) is reviewed. Ptychopeltis is definitively synonymized with Schizocrania, because new data indicate that convexity of the shell, profile of the anterior margin commissure, density of the dorsal valve costellation, ornamentation of the ventral valve and shape of the pedicle notch are worthless for separation of these genera. Four Ordovician species of Schizocrania are reported from the Barrandian area: S. multistriata (Darriwilian), S. hornyi (Sandbian), S. incola (Sandbian) and the new species S. equestra sp. nov. (Katian). Occurrence of Schizocrania striata is confirmed for the first time around the S/D boundary in the Barrandian area. Schizocrania has a wide geographic range with mid-Ordovician to early Devonian occurrences in Laurentia, Avalonia, West Gondwana and the Silurian occurrence in Baltica. Schizocrania was the earliest lingulate brachiopod adhering to floating objects in an open sea (both living cephalopods and their empty drifting shells), but it was highly opportunistic, and used any vacant hard surface on the sea floor (conulariids, strophomenid brachiopods, trilobites) as a suitable substrate for settlement of the larva. Decline of the genus coincided with disappearance of planktic graptolites, and might have been caused by competition of rapidly evolving planktic dacryoconarids, increased predation pressure, and rebuilding of the trophic structure in the early Devonian seas.

scholarly journals New Species of Terebratella, From the Bargate Stone

The Geologist ◽  
1864 ◽  
Vol 7 (5) ◽  
pp. 166-167 ◽  
Author(s):  
C. J. A. Meyer.
Keyword(s):  
New Species ◽  
Medial Septum ◽  
Short Description ◽  
Dorsal Valve ◽  
Future Time ◽  
Hinge Line ◽  
Central Division ◽  
Peculiar Form ◽  
Present Opportunity

I send some drawings and a short description of a pretty little Brachiopod from the Lower Greensand of Godalming, of which, unfortunately, I possess at present only a few single valves, viz. 7 dorsal and 4 ventral valves. These are, however, sufficiently perfect to enable me partially to describe the shell, and I take the present opportunity of so doing, with the hope that, at some future time, better specimens may come to light. (See Pl. XII. Figs. 1–6.)The species is apparently new, local in distribution, and, so far as I am at present aware, confined to the “Bargate stone” of Guildford and Godalming, the position of which is near the base of the ferruginous or upper division (of Fitton) of the Lower Greensand. From the partial outward resemblance of this shell to that of Terebratella Menardi, and from the fact of the hinge line and medial septum in the dorsal valve being of the same form in both, I am inclined to consider this species as a Terebratella: the peculiar form of the dorsal valve has suggested its specific name.Terebratella trifida, n. sp. Shell (judging from a comparison of several single valves) as wide as long, in old specimens perhaps rather longer than wide; convex in both valves: dorsal valve moderately convex, and divided into three portions; a large, elevated, mesial fold, in the shape of an acute rib, occupying the entire central division, on either side of which, on the lateral divisions, there exist one or two ribs of small elevation, followed occasionally by a third of still smaller size;

On New Brachiopoda, and on the Development of the Loop in Terebratella

The Geologist ◽  
1861 ◽  
Vol 4 (3) ◽  
pp. 96-99 ◽  
Author(s):  
Charles Moore
Keyword(s):  
Ventral Valve ◽  
Dorsal Valve ◽  
Longitudinal Groove ◽  
Considerable Portion ◽  
Longitudinal Septum

Shell inequivalve; punctuate, rather rugose, front deep, rounded; attached by a considerable portion of the ventral valve; beak slightly incurved; deltidium small and depressed. The ventral valve is flattened on its under side. Its interior is surrounded by an elevated, slightly granulated margin. Under the deltidium are seen two raised oval processes, separated by a longitudinal septum, which occupies the greater length of the shell. The exterior of the dorsal valve is rugose and flattened. The interior possesses a narrow, thin, punctuated margin, immediately succeeding which is a ridge of single granulations, which are stronger towards the frontal margin, gradually disappearing as the ridge passes upwards. Springing from the centre of this granulated ridge is a septum, slightly tapering from its base, on either side strongly serrated, between which is a central longitudinal groove. The septum occupies nearly the whole height allowed by the cavity of the shell, and divides it to nearly three-fourths of its length. From the top of the septum there are thrown off two extremely delicate lamellæ, forming a loop which curves downwards towards the front of the shell, where they bifurcate, and are then again united to the shell at its inner sides. Above the septum and attached lamellæ a band occurs, forming a bridge over the visceral cavity. This is united to the granulated ridge, which thus completely surrounds the inner portion of the valve.

On Heptaphyllum, a New Genus of Carboniferous Coral

1924 ◽  
Vol 61 (9) ◽  
pp. 416-423 ◽  
Author(s):  
Arthur E. Clark
Keyword(s):  
New Genus ◽  
Growth Stages ◽  
Lower Carboniferous ◽  
North West ◽  
The North ◽  
Rugose Corals ◽  
The Subject ◽  
The Way ◽  
West Of Ireland

A few years ago Mr. Carruthers described an aberrant coral, Cryptophyllum hibernicum, from the Lower Carboniferous of Bundoran, Donegal. Cryptophyllum occurred in the Lower Calp shales, which are considered to be about at the horizon of Vaughan's C2 to S1 beds. Another aberrant genus, Heptaphyllum, also from the north-west of Ireland—Lower Carboniferous shales, Sligo—forms the subject of this paper. Cryptophyllum is remarkable, first for the manner in which the earlier major septa appear—irregularly, and nearly simultaneously, instead of regularly, and in consecutive pairs, as is typical for Rugose Corals; and also in the development of only five septa instead of the normal six in the earliest growth stages. Heptaphyllum, as its name implies, develops seven septa in the young corallum. It resembles Cryptophyllum in having an early aseptate corallum, and in the way in which the earlier septa appear.

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