GEOLOGY. 



43 



Fig. 12.— The Gigantic Irish Deer Cervus (Megaceros) liibemicus, from shell-marl beneath 

 the peat, Ireland. 



ORDER IX. — CETACEA (Whales, etc.), and ORDER X.— 

 SIRENIA (Manatee, Dugong, etc.). 



In Wall-cases X. and XIV. at the East end of this Gallery, are 

 placed the fossil remains of the aquatic mammalia of the order 

 Sieenia and Cetacea, represented at the present day by the Dugong 

 and Manatee, and by the true Cetaceans, the whales and dolphins. 

 The Sirenians are adapted for an aquatic existence; they have a 

 powerful tail-fin placed horizontally (not vertically, as in fishes), and 

 not supported by bony rays. The hind-limbs are almost or wholly 

 wanting ; the fore-limbs are modified to form broad swimming paddles 

 or " flippers." In the form of the head they are not unlike the 

 walrus-family, but they have no large tusks, and their molar teeth are 



e 



