162 DE. J. MURIB ON THE FOEM AND STEUCTTJEE OF THE MANATEE. 



extension of the panniculus carnosus. Eapp' mentions, under the head of retractor 

 ischii, or ischio-caudalis, that he found this in the Manatee thin and weak, springing from 

 the hffimal spines of the first two caudal vertebrae and inserted into the pelvic bones. 

 I apprehend he alludes to the above-described muscle, which, as far as action and 

 attachments are concerned, is rightly named by him. If, however, we seek its homology 

 among the four-limbed and long-tailed Vertebrata, we find it representative of the ischio- 

 or mayhap ilio-coccygeus, possibly these two combined. 



Stannius regards the sphincter ani as double, inasmuch as he refers to the existence 

 of an internal and an external anal sphincter. This I have found so far true that thick, 

 fleshy, circular fibres, besides its ordinary muscular coat, surround the intestine. Above 

 the anus, and at the external orifice, these expand broadly as they become supei-ficial. 

 Virtually, less or more continuous, these may be regarded as outer and inner sphincter 

 from position. The same disposition and unusually developed condition of the anal muscle 

 is met with in Whales. In them, as in the Manatee, the gut is firmly compressed at 

 its outlet and above, leaving in the contracted condition but a very narrow orifice. The 

 fseces in these two groups are consequently of small calibre, and very different from the 

 scybalous masses of the Elephant. The lower gut in it seems altogether more capa- 

 cious ; but it is nevertheless provided with a broad muscular sphincter, as Laurillard's 

 figure shows (pi. 285, Q). 



I mention in my description of the panniculus that in the female a fleshy slip, about 

 an inch wide, is posteriorly derived from it. This offshoot of the panniculus car- 

 nosus, but most probably representing a separate perineal muscle, diverges from the 

 more backwardly extended caudal fibres about opposite the generative fissure. Di- 

 rected obliquely inwards towards the median line and posteriorly, it is inserted into 

 the fascia beneath the skin of the perineal raphe, between the vaginal and anal 

 sphincters. This muscle, although apparently a continuation of or derivative from the 

 panniculus, I regard as the homologue of the levator ani ; for, besides the dermal slip 

 in question, an additional short portion comes from the rectal surface near the pelvis 

 and joins the former. 



In the female a transversus perincei appears to be represented by a longish narrow 

 muscle springing from the inner border of the pelvis and going forwards to the outside 

 of the sphincter vaginae and inside and behind the lesser slip of the erector clitoridis. 

 In the male the levator ani and transversus peiinsei were more or less united, and with 

 a greater transverse direction of fibre. 



Other muscles connected with the generative parts in the female as follows: — a 

 sphincter vagince, consisting of a thick layer of fibres sun-ounding the vagina and 

 vestibule, and which are strongest towards the perinseum ; an erector clitoridis {E.c), 

 divisible into two slips: the external fleshy fusiform bundle arises from the apex of 

 the inner pelvic horn ; the smaller inner slip lies alongside the last, but has no pelvic 



' Op. cit. p. 83. 



