130 PEOF. W, B. BENHAM ON THE [May 21, 



The retractor penis (B) is seen to have precisely the same 

 relation in both, and the hinder moiety of the accelerators (A') 

 presents the same modification described above. But the muscles 

 for which I have used the name " ereetores penis " are in the 

 G-rampus represented by a much larger pair (B), termed by Turner 

 (and others) the " ischio-cavernosi." In this whale, each arises 

 from, and almost entirely conceals, the pelvic bone (pel.). Apart 

 from this, the relations are similar to those in Cogia. 



When removing the viscera from Cogia, I sought for the pelvic 

 bone, and not iinding it in the neighbourhood, imagined that 

 it would be concealed within the lateral ereetores ; but on dis- 

 secting these muscles I find no trace of it. I think, then, we may 

 conclude that there is no pelvic bone in Cogia. I cannot speak 

 with absolute certainty, since the body- wall was much cut about ; 

 but if it had been present it would have been connected with the 

 penis ; and there is no trace of any muscle, other than I have 

 described, which would have been attached to it. We may take it, 

 then, that the pelvic bone is absent, and that the " ereetores " are 

 homologous with the m. ischio-cavernosi. 



At first sight, the account and figure given by Struthers from 

 the Greenland Eight Whale differs considerably from the other 

 two Cetacea. On the ventral surface (text-fig. 8) there is a great 

 muscular mass consisting of a right and left half, sepai-ated by a 

 median raphe or septum. This mass is subdivided into an anterior 

 (J5) and a posterior {A) muscle by a " horseshoe-shaped septum " 

 (/S). To this great muscle he gives the name " compressor." 

 The anterior compressor consists of fibres with various origins, 

 but with in general an antero-external direction, as seen from 

 below. The hindmost fibres arise from the inner surface of the 

 hinder part of the pelvic bone (as in the case of the mus. ischio- 

 cavernosus in the Grrampus) ; they pass forwards to be inserted, 

 on the dorsal surface, into the median septum or raphe : the 

 deeper fibres are inserted in the outer surface of the crus penis. A 

 second lot of fibres arise on the ventral surface from this septum 

 and pass round the corpus cavernosum to be inserted in its 

 dorsal surface : these, in fact, surround the base of the corpus 

 cavernosum. 



On p. 306, the author goes on to say : — " This vast muscle in 

 Mysticetus corresponds to two muscles in human anatomy : the 

 part from the inner slope on both aspects of the [pelvic] bone to 

 the erector penis (ischio-cavernosus), enormously developed ; the 

 part from the mesial raphe, on the under surface, to the anterior 

 part of the accelerator urinse (bulbo-cavernosus)." 



Before giving reasons for controverting this view, I will continue 

 his account (p. 307) of the posterior part of the great compressor 

 (A) behind the horseshoe-shaped septum. 



Its fibres are only visible from the ventral aspect ; they arise 

 from the median raphe, pass foi'wards and outwards, towai'ds the 

 horseshoe-shaped septum, and "are inserted into the whole fibrous 

 surface covered by this muscle : tJie deeper into the fibrous coat 



