310 MAMMALIA. 



prsemaxillaries, often asymmetrical. Spiracle semilunar. Hyperoodon, biden* 

 Flem., more than twenty feet long, North Atlantic Ocean. 



Fam. Catodontidae Physeteridae (Sperm-whales). Head of enormous size f 

 being one third of the length of the body. Swollen to the extremity by the 

 accumulation of fluid fat (spermaceti). Upper jaw without teeth. Kami 

 of the lower jaw applied to one another and armed with a row of conical 

 teeth. Spiracles separate. They live on Cephalopoda. Catodon inacrocepJialus 

 Lac., Cachelot, forty to sixty feet long, North Sea ; Physeter tursio Gray, 

 North Atlantic Ocean. 



Tribe 2. Mysticete (Whalebone Whales). Head very large, jaws 

 without teeth, with whalebone (fig. 673). (Esophagus narrow; 

 spiracles separate. 



Fam. Balsenidae. Cetacea of considerable size, with enormous hoad, wide 

 slit-like mouth without teeth, and double nasal openings ; with very small eyes 

 near the angle of the mouth. Two rows of horny transverse plates, frayed out 

 at their lower edges, arise from the palate and upper jaw. These are the 

 whalebone plates. They project vertically into the mouth, are closely packed 

 together one behind the other, and decrease in size anteriorly and posteriorly 

 They form a kind of sieve, which when the huge mouth is closed retains the 

 small Medusae, Nudibranchs, etc., which are taken in with the sea water, while 

 the water flows out. Balanoptcra, Korquals ; B. rostrata Fabr., North Sea ; 

 Balcena, mysticetus, Greenland Whale, reaches a length of sixty feet. 



Sub-order 2. Cetacea herbivora, Sirenia. With thick, sparsely 

 bristled skin, swollen lips, and anterior nasal apertures, with 

 pectoral mammae. The large fins are movable at the elbow joint, 

 and end like hands with traces of nails. Neck distinct. Dentition 

 and internal organisation approximate to those of the Ungulates. 

 The incisors are replaced. The grinders have a flat crown, and are 

 always well developed in both jaws. There are no canine teeth. In 

 the Dugong there are two tusk-like incisors in the upper jaw, while 

 the lower incisors fall out early. They feed especially on fuci and 

 seaweed on the sea coast. 



Fam. Sirenia. Nasal openings placed far forward. Manatus Australia 

 Tils., American Manatee. Found at the mouths of the Orinoco and Amazon ; 

 M. senegalensis Desm., African Manatee ; Halicore indica Desm., Dugong, 

 Indian Ocean and Kca Sea; Rhytina Stelleri Cuv., Steller's Sea-cow, 

 extinctt 



