THE EXTERNAL FORM OF IV HALES 31 



DERMAL SKELETON 



In smooth-skinned creatures like whales, without 

 anything more than at most a vestige of the original 

 mammalian hairy covering, it may appear at first 

 somewhat unnecessary to devote a section to a sub- 

 ject with such a title as that selected to head the 

 present page. Nevertheless, the interesting fact is 

 true, that in two whales, at any rate, among living 

 forms, considerable traces of a dermal armature exist, 

 which seems to be fairly interpretable as a remnant 

 of what seems to have been a more extensive 

 armature of a similar kind in certain of the extinct 

 Zeuglodonts. Some years ago (in 1865) the late 

 Dr. Gray descried from the shores off Margate a 

 porpoise, which he regarded as new, and described 

 under the name of P/ioccena tiLberculifera, on account 

 of the fact that it possessed "a series of spines on 

 the upper edge" of the dorsal fin. Dr. Gray was 

 not then aware that the same character occurs in 

 the common Porpoise, that it had been noted so 

 long ago as Pliny. The common Porpoise, in fact, 

 is marked by this character, as is also Phoc&na 

 spinipinnis of Burmeister, and the allied, if not 

 identical, genus Neomeris phoc&noides. The latter 

 animal has a more extensive series of these tuber- 

 cles, which have been fully described by Kiikenthal.* 

 There are several rows of them running along the 

 back (this genus has no dorsal fin), from not far 

 behind the head to a point not remote from the 



* " Walthiere," in Denkschr. Mcd.-Nat. Gcsclls. Jena, 1889. 



