Ages isotopiques K/A de roches prelevees dans les possessions francaises du Pacifique

The authors present some forty age determinations made by the K/Ar method on the volcanic rocks of Tahiti and the archipelagoes of French Polynesia by means of a Philips omegatron. The results obtained may be divided grossly into three groups: sub-Recent ages (from 0 to 3 m.y.); Mio-Pliocene ages (about 10 to 15 m.y.) and an age of about 150 m.y., given by a granular inclusion in a nephelinic gabbro-diorite from the center of the island of Tahiti. The last age is particularly interesting because no fossiliferous formations older than Cretaceous are known in the Pacific. These rocks may thus be older and may date at least from the Jurassic. They accordingly pose the problem of the existence, beneath the present volcanoes, of a much older crystalline basement.

On Microstrongylus genetiæ gen. and sp. nov., a Trichostrongyle Parasite of Genetta senegalensis

A Considerable number of specimens of this parasite were collected from the small intestine of a genette which died in the Gardens of the Zoological Society of London.The cuticle of the cephalic extremity is dilated anteriorly. This swelling is terminated posteriorly by the cuticle incurving to meet a raised ring on the body-wall, about the level of the junction of the anterior and second fifths of the œsophagus. There are no cervical papillæ present, and it is probable that this ring may be regarded as replacing them. Just anterior to the middle of the œsophageal region and at the level of the excretory pore is a cervical groove which completely encircles the body. Laterally the cuticle on the anterior margin is thickened; it is also thickened on the ventral side, but less so than laterally. These thickenings are reinforced by a granular inclusion in the cuticle. The posterior margin is thickened only in the region of the excretory pore.