SYSTEMATIC REVISION OF THE SUBORDER. 39 



Its outline is transverse at the middle and truncate at each lateral extremity. A large 

 supracondylar foramen pierces the basal part of the distal expansion near the inner 

 border. The opposite edge is strongly grooved longitudinally, the groove being 

 bounded in front by a prominent crest, which sinks just proximal 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 opposite direction, 

 /. ^., 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 remark- 

 able 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 portion includes the inferior part of the acetabulum. In C. iiatalis 

 the anterior apex is below the middle line of the pubes near their anterior border. 

 In the same species there is an additional small 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 trochanter 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 moderately elongate, and are depressed. The claws 

 are curved and compressed below." 



On page 528 of the same article a table is given showing the charac- 

 ters of the humerus of Clepsydrops in contrast with those of other animals 

 of the same formation. 



Despite the frequent tise of the name Clepsydrops by Cope, his numer- 

 ous descriptions, and the labels in the collection, it is impossible to fix on 

 any characters used by him in the identification of specimens, beyond the 

 small size and the lack of condyles on the limbs. His frequent identifica- 

 tions of vertebrae as belonging to this genus are not justified by his descrip- 

 tions or direct comparisons. They are mostly D. incisivus. 



Revised description of genus : 



(i) Diastemal notch present, slight and filled with smaller teeth. 



(2) Maxillary canine and incisor teeth enlarged. 



(3) Teeth with cutting edge. Not crenate (?). 



(4) Neural arch of vertebrae free in young, coossified in adult. 



(5) Vertebrae with changing length in different parts of column (?). 



(6) Anterior dorsals with the intercentral face on the anterior face of the 



centrum and sharp keel. 



(7) Spines vertical, slightly recurved in posterior lumbar region. 



(8) Character not shown. 



(9) lyimb bones without well-developed articular faces. 



(10) Humerus without prominent entepicondyle or ectepicondylar notch. 



(11) Abdominal scutes absent (not observed). 



(12) Tail very long and slender. 



(13) I to 1.3 meters long. 



