162 DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 
extension of the panniculus carnosus. Rapp' mentions, under the head of retractor 
ischii, or ischio-caudalis, that he found this in the Manatee thin and weak, springing from 
the hemal spines of the first two caudal vertebra 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 superticial. 
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 
feces 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 (pl. 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 Jevator 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 perinei 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 vagine and inside and behind the lesser slip of the erector clitoridis. 
In the male the levator ani and transversus perinei 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 vagine, consisting of a thick layer of fibres surrounding the vagina and 
vestibule, and which are strongest towards the perineum; an erector clitoridis (£.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 
1 Op. cit. p. 83. 
