152 PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



authentic record. In its development it occupies a place half way between the 

 true Equus and the earlier three-toed horses. It is distinguished from these 

 ancestors by the absence of its lateral digits, but from the modern horse by 

 the full length splint bones and by the complete ulna, which through its middle 

 portion is less than an eighth of an inch in diameter. A large preorbital pit, 

 which probably marks the location of a scent gland, appears to separate it 

 from Equus, but allies it with several of the earlier types. 



The associated fauna — Mastodon, Teleoceras, Merycodus, Protohippus, etcet- 

 era — indicate a very late Miocene or an early Pliocene age. 



The individual had just come into full possession of its milk teeth, indicat- 

 ing that it was less than a year old. The completeness of the specimen and 

 its various unique characters make it a very interesting contribution to science. 



Discussion by Professor Osborn, Mr. Gidley, and the author. 



Session of Thursday, December 30 



Thursday morning, at 9.30 o'clock, the Vertebrate Section met for the 

 completion of their program, Dr. F. B. Loomis presiding and Dr. W. K. 

 Gregory acting as secretary. 



PRELIMINARY REPORT OF THE COMMITTEE ON THE NOMENCLATURE OF 

 THE SKULL ELEMENTS IN THE TETRAPODA 



BY W. K. GREGORY 



(Abstract) 



The committee, consisting of Professor Williston (chairman), Doctors Case. 

 Moodie, Watson, Broom, Gregory ( secretary ) , had considered the nomencla- 

 ture and homologies of the skull elements of the Permian reptiles and am- 

 phibians and modern mammals, and were in process of drawing up an alpha- 

 betic list of preferred names with synonyms. The principles of selection 

 advocated by the committee were set forth and the homologies of the "alis- 

 phenoid" and other elements were discussed. 



Kemarks by Doctor Case and Professor Scott. 



ORIGIN OF THE STERNUM IN THE REPTILES AND MAMMALS 1 

 BY S. W. WILLISTON 



(Abstract) 



From the evidence afforded by Permian Tetrapoda, the author concludes thai 

 the sternum of reptiles and mammals had been derived from the abdominal 

 ribs. 



Discussion by Doctor Case, Doctor Gregory, and Professor Scott. 



1 Read by F. B. Loomis in the absence of tbe autbor. 



