DR. J. MURIE ON THE ORGANIZATION OF THE CAAING WHALE. 289 



vagina, and thence directed outwards and slightly backwards is attached to the fascia 

 in front of the os innominatum. The second fleshy band is situate immediately in 

 front of the last, the two being in close union. Anteriorly it has the same derivation, 

 but posteriorly proceeds along the outer margin of the os innominatum almost to the 

 middle. 



This pair of muscles serves much the same office, viz. seem to draw inwards, or are 

 protractors of the pelvis, and, through continuity by fascia across the urethra, may 

 constrict this canal. As regards theii- homology, they bring to mind the two portions 

 of Wilson's and Guthrie's muscles, the so-called compressores urethrse, or transverse 

 and perpendicular constrictores urethras. Possibly they may include the circular fibres 

 of San torini, = stratum internum circulare of Miiller, if we take into account along 

 with them their fellows of the opposite side. In studying the parts, I imagined for a 

 time that the larger of the said muscles might be the representative of a pyramidalis. 

 On the other hand there is more reason to believe them very fully developed urethral 

 constrictores. Hence it is most interesting to find in Cetacea parts so manifest which 

 n Man are mere rudimentary structures. 



Deeper than the four preceding there is another muscle, which, without doubt, is a 

 true sphincter vaginae, =bulbo-cavemosus in the male. It is exceedingly large, fleshy, 

 and powerful. It is attached to the vagina near the anterior end of the pelvic bone, 

 and, as a broad fleshy mass, encircles the generative canal, beneath the mammary gland. 

 Broadest in front, as it narrows behind it becomes inserted on the strong median fascia 

 posterior to the vulva. 



I may next call attention to a. small slip of muscle which bridges between the pos- 

 terior comer of the os innominatum and the recto-pelvic fascia. Springing from the 

 inner deep margin of the bone, it crosses inwards and slightly forwards towards its 

 narrower insertion. It lies upon the broad belly of the combined lumbo- and ilio- 

 coccygeus, and is covered by the erector clitoridis and compressor mammae. The 

 action of this diminutive muscle evidently is to pull each pelvic bone inwards from 

 behind or, contrariwise, to render tense the pelvic fascia. 



It appears to me to be the homologuc of a deep transversus perinei. 



Finally, I shall refer to a long, elliptical, fleshy and powerful perineo-caudal muscle. 

 This in Glohiocephalus, as in Gramims (1), is double-headed ; or if considered two 

 muscles, these are conjoined behind. It or they best comply with the pubo- and ilio- 

 coccygeus of other mammals, which I am convinced is the true homology. If I under- 

 stand aright, Stannius terms it retractor ischi in Phocmna, and Rapp ischio-caudalis. 

 In the female Caaing Whale the narrow outer portion springs from the outer border of 

 the posterior third of the os innominatum, thence goes backwards as a fleshy riband to 

 the outside of the next. This much more bulky but also fleshy portion commences 

 from the under surface of the deep pelvic fascia, and trends straight backwards along 

 the middle of the narrowing portion of the caudal region. It has the rectum between 



