36 



have no 'vesiculse 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. The ' right whale ' of the 

 northern hemisphere (Balcena mysticetus) is represented by a 

 distinct species (Balo&na australis) in the southern hemi- 

 sphere : the high temperature of the waters at the equatorial 

 zone bars the migration of either from one pole to the other. 

 True Cetacea feed on fishes or marine animals. 



The second order, called SIEENIA, have teeth of different 

 kinds, incisors which are preceded by milk-teeth, and molars 

 with flattened 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 mamma3 are pectoral ; 

 they are ' testiconda,' but have 'vesiculae seminales.' The 

 Sirenia exist near coasts or ascend large rivers ; browsing on 

 fuci, water plants, or the 1 grass of the shore. There is much 

 in the organization of this order that indicates its nearer 

 affinity to members of the succeeding division, than to the 

 cetaceous order. 



The Dugongs (Halicore) inhabit the Eed sea, the Ma- 

 layan Archipelago, and the soundings of the Australian 

 coasts : the Manatees (Manatus) frequent the shores of tropi- 

 cal America and Africa. 



In the Ungulata the four limbs are present, but that por- 

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

 which blunts its sensibility and deprives the foot of prehen- 

 sile power. With the limbs restricted to support and loco- 

 motion, the Ungulates have no clavicles; the two bones of the 

 fore leg are fixed together in the position anatomists call 

 'prone;' as a general rule hoofed quadrupeds feed on vegetables. 



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

 by fossil remains of certain South American genera, e. g. 

 Toxodon and Nesodon, with long, curved, rootless teeth, 



