218 TEETIAET VEETEBEATA OF THE EATtM. 



C. lOOal. Imperfect right humerus, very short and stout, but shape altered by adherent matrix. 

 Length 13 "4 cm. 



M. 9239. Proximal end of a large humerus described above. Long diameter o£ head 5'1 cm., short 

 diiimeter of head 4"5 cm. Presented hy W. E. de Winton, Esq., 1903. 



M. 9240. Distal end of a large humerus, much abraded. Total width 7 cm., width of articular 

 surface 4*3 cm. Presented hy W. E. de Winton, Esq., 1903. 



Order CARNIVORA. 



The Carnivora are only represented in these deposits by members of the primitive 

 group — the Creodonts, but traces of several genera of these, all referable to the family 

 Hyaenodontidse, have been found. One interesting point is, that certain of the 

 limb-bones indicate that some of these animals lived an aquatic or semi-aquatic life. 

 One humerus (C. 9445) is practically identical in form with that of Lutra, or still 

 more with that of the probably more aquatic Potamotherium. The occurrence of such 

 aquatic Creodonts is of considerable interest in view of the possible origin from them 

 of the Pinnipedia. The conditions under which the Sirenia originated from primitive 

 semi-aquatic Ungulates, probably Proboscidean, would be precisely those under 

 which semi-aquatic Carnivores might be expected to become modified in the direction 

 of the Pinnipedia, a group which some writers regard as having arisen directly from 

 the Creodonta. 



Family HY^NODONTID^. 



This family, as defined by Wortman*, is here represented by three genera — Pterodon, 

 Apterodon, and Sinopa (or a very closely allied form), which are all known from other 

 regions. The first lower molar is relatively small and weak, and the most specialized 

 lower carnassial tooth is the third molar. The isolated limb-bones that have been 

 found can only be referred provisionally to any particular species. 



Genus HY^NODON, Laizer & Parieu. 

 [Comptes Eendus, vol. vii. (1838) p. 442 ; also Ann. des Sc. Nat. [2] vol. xi. p. 27.] 



Third upper molar wanting; first and second without antero-internal cusps ; posterior 

 lobe (metastyle) forming a cutting-blade larger than the anterior lobe. Lower molars 

 with neither postero-internal cusp nor talon. 



* " Studies of Eocene Mammalia in the Marsh Collection, Peabody Museum," Amer. Journ. Sci. [4] 

 vol. xiii. (1902) p. 433. 



