1901.] A]SrATOMT OE COGIA BEEVICEPS. 131 



of the bulb ^ ; the most superficial into the hinder surface of the 

 horseshoe-shaped septum ; the intervening and greater part into 

 the hard fibrous coat of the crus." 



Behind this muscle he represents a gi'oup of curved fibres 

 (A', fig. 2), the ends of which arise from the horseshoe-shaped 

 septum in front ; the right and left by a median raphe. These 

 cross over behind the retractor penis. To this muscle he gives 

 the name — with some hesitation owing to the mutilation — " levator 

 ani" (p. 308). 



This " horseshoe-shaped septum " is a vertical sheet of fibrous 

 tissue, attached to the lower faces of the crura penis and of the 

 bulbus spongiosi. " In sections the septum appears as a prolonga- 

 tion of the special fihrous stratum ivhich thickens the under surf ace of 

 the crus^, and may be regarded as a continuation of that stratum, 

 shelving to the surface in relation to the attachment and action 

 of the posterior compressor muscle " (p. 306). 



From the relations of the " anterior compressor " (B) — that part 

 which lies in front of the horseshoe-shaped septum — it seems to 

 me that, not merely one part of it, but the whole is homologous 

 with the erector penis or ischio-cavernosus, while the " posterior 

 compressor" (A) is nothing else than a much reduced " accelerator 

 urinse" ; for, like it, it is related to the corp. spongiosum, and the 

 account of its attachments agrees with that given by Sir W. Turner. 

 Further, the so-called " levator ani " (A ') has relations practically 

 identical wdth the " posterior moiety" of the accelerator. 



As to the horseshoe-shaped septum, it seems to correspond with 

 the longitudinal septum that, in Cogia, separates the acceleratores 

 from the erectores (PI. XI. fig. 20, 2), which, owing to the short- 

 ening of the median muscle and the great development of the 

 lateral ones, has assumed this curved form. 



A comparison of the arrangement in the three genera shows the 

 same two pairs of muscles in each, but an interesting disproportion 

 in the relative sizes. At one end of the series, Cogia, we find the 

 accelerators {A) relatively enormously developed, probably in re- 

 lation to the bifurcation of the corp. spongiosum ; at the other 

 end of the series, in B. mysticetus, the accelerator is much reduced, 

 while the erectores (B) are enormously developed — no doubt in 

 relation to the great size of the pelvic bone and to the existence of a 

 rudiment of the hind limb, both of which are absent in Cogia. 

 The Grampus occupies a middle place in the series, in which a 

 pelvic bone is present, but with neither a hind limb nor crura c. 

 spongiosi. 



List of Papers referred to in the text. 



1. Beatjeegaed & BouLAET. — " Sur FUtricule prostatique et les 

 Canaux deferents des Cetaces." C.E. Ac. Sc. vol. 119, 1895, 

 p. 596. 



^ Note. — The italics ai-e mine. 



