AQUATIC MAMMALS 



crete a thick, apparently sticky, pinkish substance which formerly gave 

 rise to the belief in the blood-sweating proclivities of this behemoth of 

 holy writ. This is presumably accomplished for the purpose of furnish- 

 ing a protective covering to guard against dessication of the hide, but 

 for all we know to the contrary it may also function in fitting the skin 

 for lengthy submergence. 



It was at one time argued by several investigators (as Abel) that a 

 number of bony plates discovered associated with the remains of a 

 zeuglodont constituted a part of a dermal armor, but it was later shown 

 that these plates belonged to a turtle. Several other investigators, chiefly 

 Kiikenthal, have vigorously championed the theory that the series of 

 dermal dots upon the middorsum of Neomeris, and to a lesser extent 

 one or two other genera of porpoises, is a remnant of a dermal arma- 

 ment. Kiikenthal also found what he interpreted as dermal ossicles 

 upon the anterior margin of the flipper, and scattered over the body of 

 the common porpoise. His most significant evidence was that the dor- 

 sal rows of dots were much better defined in an embryo of Neomeris 

 than in adults; but this character is individually variable, for I have 

 found the dots exceptionally sharp in a young specimen and not dis- 

 cernible in another of equally tender age (Howell, 1927), nor in an 

 adult female. In none of the animals which I have examined did these 

 dots assume a squarish shape as claimed by Kiikenthal. Furthermore, in 

 preserved specimens of porpoises there is often a roughness of the skin 

 upon the anterior border of the flipper caused by the shrinking and 

 cracking of the epidermis, and it is by no means unlikely that Kiikenthal 

 was misled by his enthusiasm for his theory of dermal armature into 

 mistaking such roughness for definite ossicles. A histological study 

 showed me that the dots upon the dorsum of Neomeris are formed 

 merely by a slight thickening and local cornification of the epidermis, 

 and that it is more logical to consider them as the beginning of some 

 integumental specialization rather than as the remnant of dermal plates 

 an opinion'shared by Winge (1921). 



One would naturally presume that to a mammal highly modified for 

 best efficiency in traveling through the water the shape of the head, as 

 the part of the body which chiefly has the function of cleaving this ele- 

 ment, would be of paramount importance. In our inquiry regarding 

 what shape of head is best fitted for this use one naturally turns to the 

 Cetacea as being the mammals most highly modified for an aquatic life, 

 but from them we can learn but little. It is, of course, a self-evident 

 fact that an animal with a pointed snout which tapers gradually to a 



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