0. C. Marshr—New Fossil Reptiles, 



Art. "LTYl.— Notice of some new Fossil Reptiles from the Creta- 

 ceous and Tertiary Formations; by 0. C. Marsh, Professor of 

 Paleontology in Yale College. 



The remains briefly described in the present preliminarv 



^\;*-^re collected by the Yale College party during their 



•M-ns last summer in the Rocky Mountain region. The 



I- from the Cretaceous formation are of gi-eat interest, 



mrther illustrate the remarkable development in this 



V^ \'Oth in numbers and distinct forms, of the Mosasau- 



ioi«i Reptiles, which appear to have been comparatively rare in 



other parts of the world. Fortunately, moreover, some of these 



remains serve to clear up several obscure points in the structure 



"1 tiit'se reptiles, and prove conclusively that they had a well 



' ■ ' I'll pelvic arch and posterior limbs; although up to the 



'lue no satisfactory indication of this had been discov- 



; the eminent paleontologists who have recently made 



iiials an especial study consider them probably desti- 



•^ •■• -le remains found in the iWiary 



"q"_»sits are also of importance, since they show that types of 

 tfP^'li?^ life, almost unknown hitherto from that formation in 

 toe West, were, in one of the ancient lake-basins at least, 

 abundantly represented there during that period. 

 Cretaceous Reptiles. 

 Fdestosaurus* dispar, gen. et sp. nov. 

 This genus, which so far as now known includes but two 

 species of small Mosasauroids, is especially distinguished from 

 Uic/asfe, Its nearest ally, by the insertion otthe pter^^goid teeth, 

 ^aich are pleurodont in the anterior half of the series, and in 

 f posterior portion have the outer dental margin protected by 

 " "^^^ parapet of bone. From Platecarpus, the genus is widely 

 ' )y the zygosphene articulation of the vertebrae. The 

 '' and posterior limbs were well developed, but there 

 '■'itly no sacrum. 



■^(^nt species is mainly established on the more impor- 

 ■ ; ^ of a skeleton, including the greater portion of the 

 , '"-^th quadrates, about seventv vertebrce, parts of the 

 ,, ; r'l'iir and pelvic arches, and fragments of the limbs._ The 

 i^f .'^'"^ are m an excellent state of preservation, and indicate a 

 liear'th?'-!*^^ i-eptile, apparently about thirty feet in length, or 



Til ^ ^^^® of Clidastes iguanavus Cope. 

 In tK ^'^^^^^^se possess the complete zygosphene articulation. 

 wt.„°^.^^y.^<^a]s and anterior dorsals, the cup and ball are some- 

 mcimed; in the posterior dorsals and lumbars, less so; 



* EdecTT/c, devourer, and laipoc, lizard. 



