CETACEA. 



309 



but possess whalebone on the palate, feed on small marine anim.-ds, 

 nudibranchiate Molluscs and Medusa. The Dolphins, with their 

 uniform carnivorous dentition, feed on larger rishes ; the Sirenia, 

 which are intermediate, so far as their form is concerned, between, 

 the Whales and Seals, are herbivorous. Fossil remains are found 

 in the older tertiaries. 



Sub-order 1. Cetacea carnivora (True Whales). Either with 

 conical teeth in the jaws or with whalebone on the palate. The 

 nasal apertures are placed on the forehead. The larynx projects 

 like a pyramid into the posterior naves. The inamm.e are placed on 

 the inguinal region. The skin is devoid of hairs, and beneath it is 

 a thick layer of fat. The limbs are movable at the shoulder 

 joint only ; their constituent bones are rigidly and immovably 

 connected. 



FIG. 689. Delphinus delphis (regne animal). 



Tribe 1 . Deilticete (Toothed Whales). Carnivorous Whales which 

 feed principally on fish, with conical teeth in both or only in one 

 jaw. Dentition moin^tli //<><J<>i/f. Head of proportionate size. Nasal 

 apertures often united to a single sernilunar opening. 



Fam. Delphinidae. Both jaws with similar conical teeth, but nut always 

 armed ah ing their whole length. Nasal apertures united to a semilunar 

 spiracle. Plinc'iiu cam unmix Less., Common Porpoise, four to live feet long, 

 ascends the mouths ^of rivers, lives on Fishes. European seas. Bdunn 

 (Drlnhinafitfiiis) Icnr/ix Gray. White Fish : GlobiocvplialuR itli-l>ii-i'j>* ( 

 iila !; Fi.-h. North Atlantic Ocean ; Dcljiliiinix ilrlplii* L.. (.'uinmon Dolphin 

 (fio-. 689). 



Fain. Monodontidae ( Narwhals). Upper jaw with only two anteriorly directed 

 teeth which in the female are small : but in the male one of them (usually that 

 of the left side) becomes a colossal, spirally grooved tusk. The other small 

 teeth of both jaws fall out early. JfoHwfott nioinireros L., Narwhal. North 

 Polar Sea. twenty feet long. 



Fam. Hyperoodontidae. With elongated beak-like snout, only one or t\vn 

 fully developed teeth on each side in the lower jaw. Facial bones, especially 



