26 PROFESSOR OWEN ON THE CHARACTERS, ETC. 



The first order, called Cetacea, in this division are either eden- 

 tulous or monophyodont, and with teeth of one kind and usually of 

 simple form. They are testiconda and have no ' vesiculae seminales.' 

 The mammae are pudendal ; the placenta is diffused ; the external 

 nostrils — single or double — are on the top of the head, and called 

 spiracles or "blow-holes." They are marine, and, for the most 

 part, range the unfathomable ocean ; though with certain geogra- 

 phical limits as respects species. They feed on fishes or marine 

 animals. 



The second order, called Sirenia, have teeth of different kinds, 

 incisors which are preceded by milk-teeth, and molars with flat- 

 tened or ridged crowns, adapted for vegetable food. The nostrils 

 are two, situated at the upper part of the snout ; the lips are beset 

 with stiff bristles ; the mammae are pectoral ; the testes are abdo- 

 minal, as in the Cetacea, but are associated with vesiculae seminales. 

 The Sirenia exist near coasts or ascend large rivers ; browsing on 

 fuci, water plants or the grass of the shore. There is much in the 

 organization of this order that indicates its affinity to members of 

 the succeeding division. 



In the Ungulata the four limbs are present, but that portion of 

 the toe which touches the ground is incased in a hoof, which 

 blunts its sensibility and deprives the foot of prehensile power. 

 With the limbs restricted to support and locomotion, the Ungu- 

 lata have no clavicles : the fore-leg remains constantly in the state 

 of pronation, and they feed on vegetables. 



A particular order, or suborder, of this group is indicated by 

 certain South American genera, e.g. Toxodon and JVesodon*, with 

 long, curved, rootless teeth, having a partial investment of enamel, 

 and with certain peculiarities of cranial structure : the name 

 Toxodontia is proposed for this order, all the representatives of 

 which are extinct. 



A second remarkable order, most of the members of which have, 

 also, passed away, is characterized by two incisors in the form of 

 long tusks ; in one genus (DiiwtJierium) projecting from the under 

 jaw, in another genus (J?lej)Jias) from the upper jaw, and in some 

 of the species of a third genus (JSLastodoii) , from both jaws. There 

 are no canines ; the molars are few, large and transversely ridged ; 

 the ridges sometimes few and mammillate, often numerous and 

 with every intermediate gradation. The nose is prolonged into a 

 cylindrical trunk, flexible in all directions, highly sensitive, and 

 terminated by a prehensile appendage like a finger : on this organ 

 * Philosophical Transact ions, 1853, p. 291. 



