Description of a Species of Caligus. 255 
several muscular bands, which connect the opposite crenations ; in 
their contraction the crenations are rendered more prominent. 
These muscles are connected by other slender muscles irregularly 
arranged, which contract the stomach longitudinally. The lateral 
portions of the stomach are connected on each side with the shell 
adjoining, by ligamentous or cellular attachments, as is represented 
in fig. 9. ‘There is no valve between the stomach and the intes- 
tine, and when the peristaltic motion is reversed, as often happens, 
the fluids frequently return into the stomach. 
_ The intestine, at its commencement, is between three and four 
times the diameter of the esophagus, and about one fifth the di- 
ameter of the stomach. It is slightly enlarged below the second 
pair of natatories, where there are two pairs of glands, contracts 
again as it passes below the apron, and thence continues of uni- 
form size to the rectum. Its structure is very similar to that of 
the stomach, both in its inner and outer coat. The arrangement 
of its muscles in regular bands is represented in fig. 11; during 
their action the canal is crenated as in the figure. The intestine 
is attached by distinct ligaments at several places; near the 
glands, d, and the glands, e and f, we have distinctly seen these 
attachments. 
The rectum occupies the terminal half of the last abdominal 
segment, and is about one half the diameter of the intestine. Its 
communication with the intestine, is closed in the natural state of 
the parts. This rectum, if it may be so called, appears to have a 
longitudinal opening below, extending its whole length and its 
walls are usually in close contact. The external opening or anus 
is situated at its extremity. 
This portion of the alimentary canal is opened laterally by 
seven pairs of slender muscles. The first pair at the extremity 
pass directly outward along the margin of the joint; the second 
are inserted near the extremity, and pass upward and a little 
outward. The following three pairs, are attached near the mid- 
dle, and pass outward and a little upward; the remaining two 
pairs, are inserted near the opening to the intestine, and have the 
same direction as the last. ‘The muscles have often been seen in 
action, in expelling the feces; the two sides move either simulta- 
neously or alternately, according to the necessity of the case, in 
the act of expulsion. 
