448 0. a Marsh— New Fossil Reptiles from 



and in the anterior caudals they are nearly, but not quite. 

 vertical The articular faces in the cervicals are a broad trans- 

 verse oval, faintly emarginated above for the neural canal. In 

 the dorsals and lumbars the cup continues transverse, and the 

 emargination is deeper, but in the anterior caudals the outline 

 becomes a vertical oval. The posterior lumbars have the faces 

 hexagonal, with both the upper and lower borders excavated. 

 the latter due to the concave inferior surface of the centrum in 

 this part of the series. The rim of the articular ball in all the 

 vertebrse preserved is surrounded by a distinct, but not di>ep, 

 double groove. The chevron bones are coossified with the 



a notch in its posterior margin directly above the meatal pit 

 The postero-superior process is shorter, with a compressed free 

 end. The teeth are curved, and somewhat compressed. The 

 enamel is smooth, and shows faint indications of broad facet? on 

 the basal half There appear to have been thirteen mandibular 

 teeth, with alveolae for two more. The splenial extends forward 

 to the base of the seventh tooth from the front. The pterygoid 

 bones were separated, except perhaps at their anterior inner 

 margin. There were at least fifteen pterygoid teeth. The 

 crowns are smooth, with distinct posterior cutting edges. 



There is a remarkable difference in size between the cervical 

 vertebrse and those of the lumbar region, where the centra reach 

 their maximum. Although the series is here apparently com- 

 plete, there are no indications of a sacrum. The discoverv d 

 the nearly entire pelvic arch with these vertebra?, and the pres- 

 ervation, also, of the corresponding anterior arch, throws much 

 new light on the nature of the limbs in this group of reptiles. 

 These specimens clearly indicate that the bones forming this 

 portion of the skeleton in the Mosasauroids have not unlre- 

 quently been incorrectly assigned, and that two at least of the 

 allied genera, viz : Clidastes and Liodan, also possessed effective 

 posterior limbs. Several series of specimens illustrating thi? 

 are in the Museum of Yale College, and will soon be described 



at one extremity, which it contributes to form the glenoid 

 cavity, and at the other, thin and expanded. The coracoid b 

 perforated by a foramen not far from its anterior margin, i'"' 

 pelvic arch resembles that of Ichthyosaurus, and, as in t^^^*^®?*^ 

 is considerably smaller than the anterior arch. The acetabulu 



shaped, and is not unlike that in Trionyx. 



formed 



by the union of the ilium, pubis, and ischium, the first tiir- 



