ABSTRACTS AND DISCUSSIONS OP PAPERS 151 



shrubs and buds and to rapid flight from enemies ; but the fore limb presents 

 very great difficulty, since it has extremely long and slender digits terminating 

 in three laterally compressed digits with claws, somewhat resembling those of 

 tree-sloths and ant-eaters. The bones of the shoulder have, however, no fos- 

 sorial powers or musculature and were evidently incapable of digging. 



Three forms of adaptation have been suggested. First, that this arm was 

 used for pulling down branches of trees in browsing; second, that it was used 

 in scratching open ant-hills ; third, that it was used in scratching sand along 

 the seashore in search for crustaceans. None of these hypotheses appears 

 adequate or to afford a harmonious interpretation of the adaptations of this 

 remarkable animal. 



Discussion by' Mr. Gilmore and Doctor Case, the latter suggesting pos- 

 sible ant-eating habits for Ornithomimus. 



CRITERIA FOR THE DETERMINATION OF SPECIES IN THE SAUROPODS, WITH 

 DESCRIPTION OF A NEW SPECIES OF APATOSAURVS 



BY CHARLES C MOOK 



(Abstract) 



The size and structural variations of the skeletal elements in Sauropod 

 dinosaurs were discussed and the specific characters of a new species of 

 Apatosaunis were given. 



Discussion by Professor Osborn and Doctor Loom is. 



PELVIS AND SACRUM OF CAMARASAURUS 

 BY HENRY FAIRFIELD OSBORN 



(Abstract) 



A series of diagrams showing the structure of the pelvic region in Camara- 

 saurus were exhibited, with explanatory remarks, and the identity of Camara- 

 saurus and Morosaurus announced. 



Supplementary remarks by Dr. 0. 0. Mook regarding proportions of 

 pelvis. 



AN EARLY PLIOCENE MONODACTYLOUS HORSE 

 BY EDWARD L. TROXELL 



(Abstract) 



Because the modern Eqims is so intimately associated with the human race 

 there are few fossils more interesting than the remains of its ancestors, and 

 its evolution is probably better known than that of any other mammal. The 

 finding, however, of an unusually complete skeleton of PlioMppus has fur- 

 nished an additional link in the series. 



The search for fossils in the South Dakota P>ad Lands this past summer re- 

 sulted in the discovery of a one-toed horse, the earliest of which we have 



