SYSTEMATIC REVISION 



71 



dorsals a strong ridge connects the anterior and posterior zygapophyses ; 

 the parapophysis extends from another very prominent ridge just beneath 

 this so that there are two parallel ridges on the sides of the centrum in the 

 mid-dorsal series which disappear toward the caudal end. This is a very 

 prominent character and forms one of the most pronounced features of the 

 genus. In the caudal series the haemal arches are well developed, reaching 

 nearly or quite the length of the neural arches. The markings on the sides of 

 the arches, both upper and lower, are evident but much fainter than in the 

 dorsal series and much fainter than in the genera with which this one has 

 been compared. The belly was abundantly covered with abdominal scales 

 in the form of slender rods of bone, resembling in this feature again the forms 



Fig. 18. 

 Fig. 18. — CrossoUlos annulatus. No. 3040 Univ. of Michigan. X |. 



A. Three dorsal vertebrje, lateral view. 



B. The same vertebrje, superior view. 



C. Three caudal vertebra. 



D. The spines of two dorsal vertebrae, showing the close interlocking. 



E. A single dorsal or anterior caudal vertebra, showing the ridge at the base of the neural arch. 

 Fig. 19. — CrotsoUlos annulatus. Specimens in the University of Chicago. 



A. Right humerus, posterior view. 



B. Proximal and distal ends of the left humerus of another specimen. 



C. The same humerus shown in B, from the posterior side. 



D. The same, anterior view. 



mentioned above. Another point in the structure of these vertebrse is the 

 absence of sculpture and the constant presence in both the dorsal and caudal 

 series of a foramen on the side of the vertebrae; in the dorsals It occurs just 

 posterior to and below the parapophysis and in the caudals just below the 

 posterior to the anterior zygapophysis. In all the vertebrse the ends are 

 deeply cupped and the arches are coossified with the centrum. 



" Measurements. m 



"Length of one dorsal 0.0135 



Length of a second dorsal 012 



Height of the neural spine from the bottom of centrum 0205 



Length of one caudal °°9S 



Length of the chevron from the bottom of centrum 014 



Length of a second caudal o°9S 



Height of the neural arch above bottom of centrum 0165 " 



Revised description: This genus is known from the vertebrse and humeri 

 only. The foramen mentioned as occurring below the parapophysis is prob- 



