10 



VEKTEBRATA. 



No. 14. [179j Balsenodon gibbosus, Oweu. 



Cetotolite (cast). This fossil tympanic bone belongs to a large extinct 

 whale, which probably, like some contemporary quadrupeds, retained charac- 

 ters which are embryonic and transitory in existing cetaceans. It was found 

 in the Red Crag (Pliocene) of Suffolk, England; but as it is water-worn and 

 rolled, was doubtless washed out of older strata. The original specimen be- 

 longs to the Ward Collection in the University of Rochester. 



ORDER SIRENIA. 



The Sirenians resemble the Cetaceans in form and mode of life. 

 They are herbivorous and subsist on the vegetation of estuaries and 

 rivers, sometimes crawling on shore to feed-. Both jaws are armed 

 with incisors, and molars with flat-ridged crowns, adapted for 

 vegetable diet. The cervical vertebi'fe are not anchylosed as in the 

 whale. The mammoe are pectoral. There is much in the organiza- 

 tion of the Sirenians which indicates an affinity with the Ungulates. 

 They first appeared in the Eocene of Europe, and are found in the 

 American Miocene of the Atlantic region. In the Miocene Period 

 the Diigongs and Manatees were abundant and more widely dis- 

 tributed than now. Their fossil bones have the solid structure 

 peculiar to the order. The genus Rhytina has only recently become 

 extinct. 



No. 15. [175] Halitherium Schinzi. 



Skull and FEMrii (cast). This herbivorous- 

 animal, related to the Dugong, lived by the 

 sea-shore and the mouths of rivers. Remains 

 have been found in every deposit above the 

 Calcaire Grossier (Middle Eocene). These 

 specimens were discovered in the Miocene at 

 Flonheim, Rhine Valley. Size, 8x8. 



ORDER UNG-ULATA. 



This is the most numerous and comprehensive order of larger 

 mammals, both extinct and living, and includes the beasts formerly 

 classed as Ruminants and Solidungula, and all those called Pachy- 

 derms, except the Proboscidians. 



The members of this order walk on the extremity of the toes, 



