THE CETACEA. 395 



at fewest, three chambers, of whicli the first is a kind of 

 paiincli lined by a thick epithelium, while the second and 

 the third are more elongated, the last stomach being that 

 in which digestion takes place. 



The arteries and veins form great plexuses, or retia mi- 

 rabilia, and these are especially conspicuous in the cavity 

 of the thorax, upon each side of the vertebral coliimn, aoid 

 in the intercostal sj^aces. 



The soft palate is remarkably long and muscular. The 

 epiglottis and the arytenoid cartilages are more or less 

 produced, so as to give the glottis the shape of a funnel, 

 the apex of which is embraced by the soft palate, in such 

 a manner as to form a continuous air-passage from the 

 posterior nares to the larynx, on each side of which the 

 food passes. The very short trachea, before it divides 

 into the bronchi, gives off the so-called " third bronchus" to 

 the right lung, as in the Bears, Walruses and Ruminants. 



The kidneys are deeply subdivided into lobules. In the 

 male the testes always remain in the abdomen, and there 

 are no vesiculse seminales. The penis is devoid of a bone. 

 The iiterus of the female is deeply divided into two horns, 

 and the villi of the fcetus are scattered over its chorion, 

 as in other mammals with a diifuse placentation. 



The Cetacea are di"\dsible into three groups ; the Balce- 

 noidea, the Delphinoidea, and the Phocodontia.* 



a. In the Balcenoidea the nasal chambers communicate 

 with the exterior by two apertures, which are capable of 

 being shut at the will of the animal, and are called spira- 

 cles. These are not connected with any saccular dilata- 

 tions of the nasal passages, situated between the skull and 

 the integument. 



In the spinal column, no rib has a complete neck and 



capitulum, the heads of even the most anterior ribs being 



united with the bodies of the vertebrae only by ligament. 



The chief connection of all the ribs therefore, and the only 



* For further information respecting the characters of the recent 

 Cetacea, I refer the reader to Prof. Flowers' very valuable memoir 

 " On the Osteology of Juia and Ponto/icria." published in the " Trans- 

 actions of the Zoological Society for 1867." 



