CETACEANS 



86i 



hints of hind-limbs beyond mere button-hke knobs in some 

 embryos. Most forms have a median dorsal fin. Hairs 

 are generally absent, though a few bristles may persist near 

 the mouth. The thick layer of fat or blubber beneath 

 the skin retains the warmth of the body, and compensates 





-W/ 



V- 



Fig. 510. — Left fore-limb of /?rt/^wop/^/'a. Fig. 511. — Fore-limb 



of whale {Mcgaptera 

 Sc, Scapula with spine (Sp.) ; C .p., Coracord prc.cess; Innffimana) —After 

 H., humerus; K., radius; U., uhia; C, carpals em- longimana). /\iier 

 bedded in matrix ; Mc, metacarpals ; P/!., phalanges. btrutners. 



for the absence of hair. In one of the dolphins dermal 

 ossicles occur, a fact w^hich has suggested the idea that the 

 toothed whales may have had mailed ancestors. Traces 

 of dermal armour have also been found in the extinct 

 Zeuglodonts. 



The torpedo shape, the absence of external ears, the 

 absence of an eye-cleansing nictitating membrane, the 



