250 



ALLEN: NEW ENGLAND WHALEBONE WHALES. 



External M casiircmcnts of Blue Whales (after Trtie, 1904). 



Musculature. — There is no complete account of the muscular system of the Blue Whale 

 published, but it probably differs little from that of the Common Finback. A foetus of 630 mm. 

 length that I dissected had the same rudimentary finger muscles as in that species (q. v.), so 

 that Struthers' account and figures would apply equally to both. The great superficial muscles 

 are prominent in the foetus and are exposed by carefully removing the thin layer of blubber 

 (2 mm. in thickness), to which they are attached by loose connective tissue. The more dorsal 

 layer seems to correspond to a panniculus and extends as a thin sheet from a point midway 

 between the eye and pectoral limb, back nearly to the anus. It does not reach the mid-line of 

 the back, though thin fasciae extend from its upper edge nearly to the spine. Its lower border 

 forms a line joining the axilla and the anus. On the region of the forearm it passes into a tendi- 

 nous sheet that invests the upper part of the limb, but I did not discover a definite insertion. 



The entire ventral surface from the anus forward including the basal half of the jaws is 

 covered by a continuous sheet of muscle whose fibers run transversely from the lower edge of 

 the panniculus. It appears to represent the mylohyoid. A portion of this muscle is inserted 

 just behind the eye and on a level with it. In an embryo of this size the longitudinal throat 



