248 DE. J. MURIE ON THE OEGANIZATION OF THE CAAING WHALE. 



than in the old Lagenorhynchus, nevertheless offered more appearance of separation in 

 the latter {vide iigs. 63, 64, Ifl). The combined action, however, agrees, viz. protraction 

 and retraction of the lips of the blow-hole, according as the longer anterior or shorter 

 fan-shaped vertical fibres contract, and also, coincidently, compression or dilat<ation of 

 the premaxillary sac. 



A dilator naris, retractor alse nasi {seu pyramidalis plus constrictor naris, =com- 

 jiressores naris), and depressor alse nasi muscle, in superincumbent planes, besides a 

 vomerine and alar fibro-cartilages, are described by Carte and Macalister as existing in 

 Balcenoptera rostrata^. Whether they or I have interpreted the structures correctly 

 future investigators must decide. But as regards the muscles I would note that the 

 attachments and numbers of layers more truly belong to the entire facial set of land 

 Mammals than are only restricted to the homologues of the nasal group. 



3. Skin and Subcutaneous Coverings. — The skin over the entire head is very thin, 

 hardly exceeding 01 of an inch ; and the superficial film of cuticle has only a thickness 

 of about Too °^ ^^ inch. Beneath the skin proper, and corresponding to the subcu- 

 taneous tissue of other Mammals, is a dense fibro-elastic tissue, composed of innumerable 

 reticulations of white glistening fibres, intermingled with fatty or oily material. Some 

 of these fibres are stronger and more prominent than others, so that, as seen in vertical 

 section (fig. 26), there appears to be an irregular meshwork of thickish and more delicate 

 thread-like fibres laid together, warp-and-woof fashion. Some are directed longitu- 

 dinally, others transversely, and others again entwine obliquely to the cord of the nasal 

 prominence. Here and there between the fibres white puncta manifest themselves, 

 these being nothing other than cross and tangential sections of the fibrillse themselves. 



The entire body, side of the head, and throat in G. mclas has an envelope of pale 

 yellow-coloured fat, similar in consistence to that found in the same situation in the 

 Porpoise. This fat thins as it approaches the root of the tail, and upon the caudal 

 expansion is lost in the strong fibrous sulistance of which that organ is composed. 



On the body generally the fat has a depth of from 1 to 1^ inch. In some parts, for 

 example the throat and the chest between the pectoral limbs, it is even more. Where 

 the latter become free it diminishes ; and quite on these appendages it is barely recog- 

 nizable. Indeed, on the limbs strong fibrous, almost gristle-like substance takes its 

 place ; and this latter, towards the free extremity, becomes itself so reduced in quantity 

 that at the point only a very thin layer of fibro-membrane intervenes between the upper 

 and lower dark-coloured external tegument. Upon the back, in front of the dorsal fin, 

 the fatty tissue is more interwoven with fibres, and finally, in the fin, resolves itself into 

 dense, firm and elastic texture, truly more cartilage-like than fibrous. 



Regarding the function of the semirigid dorsal fin in this and some of the allied 

 genera we have not the remotest conception, unless balancing of the body in the 

 watery element has something to do with it. But it does not seem a necessary 

 ' See their chapter on its " External Nares," J. c. p. 2-38. 



