MAMMALIA. 43 



No. 172. Mastodon giganteus, Cuv. 



First Dorsal Vertebra. The original, from a Pleistocene formation in 

 the State of New York, is in the Cabinet of William's Collage, Mass. 



Size, 18x10. Price, §2.00. 



No. 173. Mastodon Borsoni, Hays. 



Eight Feitcr. From the Upper Pliocene, Department of Haute-Saone, 

 France. The original is in the Museum of Natural History at Lyons. 1 



Size, 4 ft. 6 in. x 1 ft, 5 in. Price, $8.00. 



No. 174. Toxodon atlgHStideus, Owen. 



Lower Jaw. The Toxodon, although represented only by the skull and a 

 few other fragments, has, from the earliest period of its discovery, greatly attract- 

 ed the interest and attention of Naturalists. The dimensions of its skull show 

 that it rivalled the largest quadrupeds in size, while its general proportions and 

 peculiarities of form prove clearly that this extinct genus differed essentially from 

 any other animal hitherto described. The T. appears to have united certain fea- 

 tures allying it to both tha Rodents, Pachyderms and Cetaceans. It had two 

 incisors in each side of the upper jaw, and these presented the very anomalous 

 feature of curving inwards from either side so as to form a sort of arch below the 

 palate. It is from this curving of the teeth that the generic name has been taken. 

 The T. was an herbivorous animal, and very probably fed upon the plants in riv- 

 ers like the Dugong or the Manatee. This specimen was found in the Pampean 

 formation (Pleistocene) of Buenos Ayres, and is in the British Museum. 



Size, 24x11. Price, $6.00. 



Order 8 — Cetacea. 



The members of this Order, formed for life in the ocean, have, in 

 many respects, the external appearance of Fishes. By some authors 

 they are called " Mutilates," because their hind limbs appear to have 

 been amputated. The clavicle is wanting, and the pelvis is scarcely 

 represented by two small rudimentary bones. The true Whales are 

 characterized by the extremely long bones of the face, and by the nasal 

 bones forming the very highest part of the skull. Teeth are entirely 

 wanting in the adult. The caudal vertebras differ from those of Fishes 

 in retaining the transverse processes. The true Dolphin has forty-seven 

 sharp, conical, crooked teeth in each ramus. The Sirenia are vegetable 

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

 with incisors, and molars with flat-ridged crowns. The cervical vertebras 

 are not anchylosed as in the Whale. There is much in the organization 

 of the Sirenians which indicates an affinity to the Pachyderms. 



The earliest Cetacean remains discovered are two species of 

 Priscodelphinus (Leidy) from the New Jersey cretaceous, and the 



