CONCHIOSAIIRIIS, Von Meyer.
Sp. Conchiosaurus elavatus.—The facial part of the skull is less prolonged than in Pistosaurus, and the nostrils are terminal. The teeth are twelve in number on each side, are subequal, with a pyriform crown, and are placed at widish intervals. From the muschelkalk at Laineck, near Bayreuth.
Von Meyer.
Sp. Simosaurus Gaillardoti.—The fossils, chiefly cranial, on which this genus is founded, occur in the dolomitic muschelkalk near Ludwigsberg, and in the muschelkalk of Luneville. The skull presents the large temporal fosse, the divided nostrils, and the general depressed form and compo sition of that of Nothosaurus and Pistosaurua But its facial part is much shorter ; the muzzle is neither prolonged nor terminally expanded, but forms the obtuse end of the short depressed face, of which the premaxillary part is the narrowest. The nostrils, consequently, although distant from the orbits by half the diameter of the latter, are yet nearer the fore end of the skull than in the above-cited Sauropterygian genera. The nostrils are relatively nearer to each other, the intervening bony tract being due to the premaxillaries, which, relatively to the breadth of the skull, are much narrower in Simosaurus than in Notho- or Pisto-saurus.
The profile of the skull rises from the internasal to the interorbital regions much more than in the Nothosaur, and the depth of the skull behind the orbit is greater in propor tion to its length. The post-frontals are most clearly produced backwards, along the upper border of the zygoma to the mas toids. The =Liars are co-extended, and connected with the post-frontals, but terminate freely and obtusely a little beyond the co-prolonged hind part of the maxillary, without being met by or joining a squamosal.
Most complete and extensive is the ossification of the roof of the mouth in this genus. The pterygoids are expanded into one broad unbroken imperforate flat expanse of bone, from about one-third of the distance from the snout to the occipital condyle ; they are united by a median suture, and underlap the whole of the sphenoid. The teeth, compared
with Nothosaurus, are few and large, and are subequal, save one or two at the fore and hind extremity of the series. The crown expands a little above the fang, is conical, sub-bifurcate, and impressed by a few coarse longitudinal ridges ; some are obtuse, others acute ; but all are shorter and thicker than in Notho- or Pisto-saurus.
The vertebrae have flat or very slightly concave articular surfaces on the body ; the neural arch articulates therewith by suture. In these characters, and in their general propor tions, they resemble those of Notho- and Plesiosaurus. It is significant of some difference in respect of the arrangement of the vertebrae in the same column, that although specimens from the tail, and from different parts of the back, have been obtained, no cervical vertebra with any probability belonging to this genus has yet been found. The caudal centrum presents two well-defined, rather prominent, hypapophyses for the hmal arch.
The corticoid in the contraction of the body reminded Cuvier of that of the Ichthyosaunts, but its expanded median part was differently shaped. The pubis, like that of the Plesiosaurus, resembles to a certain degree the pubis in Chelonia. The few bones of the limbs which have been found still more resemble, as do those of Pistosaurus, the corresponding bones of marine CheIonia. Accordingly, there have been entered in palaeonto logical catalogues an Iehthyosaurus Lunevillensis (De la Beche), a Plesiosaurus LunenRamis (Munster), and a CheIonia Lunevil lensis (Gray and Keferstein) ; but all these are parts of one and the same genus of Enaliosaurian, the " Saurien des environs de Luneville " of Cuvier, the " Simosaurus " of H. von Meyer.