ANATOMY OF MEGAPTERA LONGIMANA. 53 



muscular mass (c.). Along the posterior edge of the great 

 ligament is seen the posterior edge of the transversus perinei 

 muscle (d.) mostly concealed by and attached to the ligament ; 

 as broad and as thick as the palm of the hand and 6 to 8 inches 

 in length transversely. In the ring between this muscle and 

 the beginning of the levator ani muscle, is seen the retractor 

 penis muscle (e.e,) t rope-like, right and left, passing forwards on 

 the under surface of the penis ; composed of pale unstriped 

 muscular fibre, as in other cetaceans. On the great transverse 

 ligament and crus penis is seen the ischio-cavernosus muscle 

 (//.). This great muscle, 10 to 14 inches in length, 5 to 6 

 inches in breadth, and 3 inches in thickness at the middle, 

 extends still more on the dorsal aspect than on the under 

 aspect where it is seen in the figure ; when split long- ways at 

 the middle, I estimated each half as equal in bulk to an average 

 human glutens maximus. It has no direct connection with the 

 pelvic bone, its bundles passing entirely between the interpelvic 

 ligament, crura and corpora cavernosa penis. It is considerably 

 more developed, especially in breadth, in Megaptera than in B. 

 musculus. It and the transversus muscle are very much more 

 developed in Mysticetus, forming what I described and figured 

 (loc. cit., figs. 13 and 14, I. and m.) as the great compressor 

 muscle and the posterior compressor muscle. The references 

 to the muscles of the hind limb in B. musculus are from my 

 dissection of the 50-feet-long one. 



At the posterior part of the pelvic bone is the posterior or 

 caudal muscular mass (#.), as seen in section 2 inches behind 

 the bone, at least 6 inches broad by 3 inches thick. Backwards, 

 it begins to unite with its fellow in a median raphe after a course 

 of 18 inches, just behind the anus. Forwards, it is attached 

 internally to the outer part of the great interpelvic ligament 

 (c.), but mainly to the pelvic bone, to the end and for 3 

 inches on the outer side, on the outer border and both sur- 

 faces. Besides these fleshy attachments it sends forwards a 

 tendinous sheet worthy of particular notice. The outer part of 

 this sheet skirts the pelvic bone externally, and runs into the 

 anterior muscular (or tendinous) mass of the beak of the pelvic 

 bone ; its middle and inner parts after covering and thus 

 strapping down the pelvic bone, pass, the middle part to be 



