Cope.] 510 [April 5, 
The vertebree have been described elsewhere, but important additions 
to our knowledge can now be made. There are mostly small intercentra 
througbout the dorsal and caudal series, in the latter prolonged into two 
processes below, constituting chevron bones. The transverse processes on 
the dorsal and lumbar vertebrez are undivided, and on some of the dorsals, 
the ribs articulate with the centrum as well. They are present on the 
anterior but wanting on the posterior caudal vertebre. In adults the neu- 
ral arch is coéssified with the centrum, and on the lumbar and sacral re- 
gion the neural spines are greatly elevated, indicating the presence of a fin 
like that of Bastliscus. In one of the allied species the diapophyses of 
three vertebre are vertically expanded for the attachment of the ilium, but 
the centra are not codssified. 
The humerus in this genus is of remarkable character. Its proximal ex- 
tremity is expanded and regularly convex, with the articular surface at 
right angles to the sides of the bone, and not developing a head. There is 
a strong deltoid ridge or tuberosity, not extending far from the head. The 
shaft is much contracted, and the distal end is more expanded than the 
proximal. It is flattened, and supports no condyle. Its outline is trans- 
verse at the middle and truncate at each lateral extremity. A large supra- 
condylar foramen pierces the basal part of the distal expansion near the in- 
ner border. The opposite edge is strongly grooved longitudinally, the 
groove being bounded in front by a prominent crest, which sinks just 
proximad of the distal border. 
The ilium is a flat bone which contracts downwards and forwards to the 
pubis. The latter is something like the ilium in form, widening in the op- 
posite direction, 7. e. downwards and forwards. Its form is something like 
that of the Crocodilia, and it is uncertain whether those of opposite sides 
unite below. The ischium is a remarkable bone. It is greatly produced 
anteriorly and posteriorly to the acetabulum, in forming with that of the 
opposite side, a keeled boat-shaped body, which at its superior middle por- 
tion includes the inferior part of the acetabulum. In @. natalis, the anterior 
apex is below the middle line of the pubes near their anterior border. In 
the same species there is an additional smal] element between the ilium 
and pubis on the superior side at their junction. The acetabulum is formed 
by the interrupted junction of the three elements. 
The femur possesses no third trochanter, and the head and great tro- 
chanter are not separated by a neck. The little trochanter is large, and 
the condyles are well defined. The head of the tibia is expanded, and the 
fibula is well developed at both extremities. The phalanges are mode- 
rately elongate, and are depressed. The claws are curved and compressed 
below. 
The various remains of this genus now in my possession, and especially 
the skeleton of CO. natalis, show that the determinations of various parts of 
the skeleton made from isolated fragments from Illinois, were correct. 
Of the general affinities of this genus it is only necessary now to state 
that my reference of it to the Rhynchocephalia is confirmed. It differs 
