126 PROF. W. B. BENHAM ON THE [May 21, 



the longitudiual ridge of the verurnontanuin, between it and a 

 smaller lateral ridge. 



There appear, from the preliminary account by the above- 

 named authors, to be various differences in this arrangement 

 from the conditions in Dolphin and Rorqual. 



The basal region of the penis is perhaps of the most interest, 

 as we shall find striking differences in the arrangement of the 

 muscles in Cor/ia, Balcena, and Grampus. 



In the whale under consideration there are, as I have said, two 

 pairs of muscles, to which I apply the older names " accelerator 

 urinse " and " erectores penis." The two accelerators lie side by 

 side on each side of the middle line, and have a length of 7 inches 

 on the ventral surface. (PI. XI. figs. 20, 22, 24, 25, Ac, Er.) 



The fascicles of which the muscle is composed are strikingly large, 

 and have in general a transverse, i. e. circular, disposition. At 

 the extreme anterior end, the fascicles of the right and left muscle 

 interdigitate ; but for the most part they are separated by a 

 distinct median septum of connective tissue. (Fig. 20, 1.) 



By the passage of the retractor penis, the accelerators are 

 divisible into a larger anterior moiety {Ac), and a smaller posterior 

 moiety {Ac'), where the fascicles are oblique, with their mediad 

 extremities directed slightly backwards. 



The anterior moiety of the accelerator embraces and conceals 

 the cms corporis spongiosi of its side, and the fascicles are 

 arranged as follows. (See PI. XI. tig. 20.) 



Each muscle-fascicle is a broad band, thicker in the vertical than 

 in the horizontal direction (with regard to the surface of the 

 muscle), so that we may distinguish two faces and two edges, as 

 well as two ends. 



The faces are pressed against the faces of neighbouring 

 fascicles ; ono edge is directed outwards and forms the surface of 

 the muscle ; the other edge is fixed to the thin connective tissue- 

 sheath of the crus c. spongiosi. The ends are attached to the 

 vertical longitudinal septa, one of which separates the right 

 accelerator from the left (fig. 20, i); the other separates the 

 accelerator from the erector of its side (tig. 20, 2) ; and in part 

 these outer ends are inserted in the crus corporis cavernosi, with 

 which this septum is continuous. 



It is evident that the contraction of these circularly disposed 

 fibres must exert considerable pressure upon the spongy body. 



The posterior moiety of the accelerator is marked off from 

 the anterior, by the passage of the retractor penis (PI. XI. 

 fig. 23, Re.). On the ventral surface there appears to be a very 

 marked break in the muscle at this point ; but this is less marked 

 on the dorsal surface (PI. XI. fig. 25), where the transversely 

 disposed fascicles of the anterior moiety only gradually take on 

 an oblique direction ; the mediad ends are directed backwards, and 

 the last 3 or 4 fascicles enter the mass of muscle constituting 

 the " sphincter ani," but do not mix with it. They are, here, 

 inserted in a semicircular septum or sheath, concave anteriorly, 



