1884.1 ^ [Cope. 



knowledge of the osteology of this genus, and to distinguish satisfactorily 

 three species. I have much pleasure in obtaining these additional facts, 

 since everything relating to this curious genus is of interest. 



In the first place, the neural arches are not coossified to the centra, but 

 are readily separated from them. Their basis of attachment forms, on 

 each side of the median neural canal, an oblique triangular surface look- 

 ing forwards and upwards, with the apex above and behind. The ease 

 with which the neural arches separate accounts for the rarity of their 

 occurrence on separate centra. They support the diapophyses at their 

 lower border. Second, that the sacrum consists only of a centrum and 

 an intercentrum, both of which take part in furnishing a concave facet 

 for the attachment of the pelvis. Third, some of the ribs are two-headed, 

 and their capitular articulation is with the posterior edge of the intercen- 

 trum. Fourth, there is a hyposphenal articulation, as in the genera of 

 Jurassic Saurians, Camarasaurus, Amphiccelias, etc., and in the Permian 

 genus Empedias, among the Theromorpha. The hypantrum has, however, 

 this peculiarity : that its sides are produced forwards into a process on each 

 side below the prezygapophyses, each of which is subconical in form, but 

 with the interior face excavated to receive the hyposphen, so that the sec- 

 tion of the process is crescentic. These processes I have never previously 

 observed. I call them hypantrapophyses. I find them in tlie Gricotus 

 liypantricus. The neural arches of the other species are either lost or in 

 such close juxtaposition that I cannot see them. 



The species differ in part as follows ; the full characters can only be 

 given in more detailed descriptions of more perfect specimens. 



I. Dorsal iutercentra much nari'owed or pinched above. 

 Hypantrum unknown O. lieterocUtus. 



II. Dorsal intercentra equally robust above as below, or more so. 



Hypantrum unknown C. crassidiscus. 



Hypantrum with acute lateral processes C. hypantrieus. 



The measurements of the' C. crassidiscus are as follows : 



Measurements. M. 



( vertical 025 



Diameters of dorsal centrum behind \ ,,.„„„„,„„„ no- 



(. transverse 02o 



f middle line below 013 



Length of do. | ^^ ^^^^ ^^ ^^^^.^^ ^^.^1^ ^^^3 



(width 010 



Base of neural arch | j^^g^j^ ^^9 



r vertical 025 



Diameters of a dorsal intercentrum | transverse 025 



f middle line below 009 



Length of do.j .. . ^^^^^ 0^^- 



transverse length 027 



Diameters of coracoid "j f at glenoid face 029 



[width j at internal face 010 





