Description of a Species of Caligus. 243 . 
sertion of the more powerful of the abdominal muscles below the 
centre of this segment, in preference to an attachment near its 
base, enables the animal to give this segment great flexion. When 
the animal has been attached to the glass out of the water, we 
have often separated the anterior portion of the body from the 
glass, till it formed an angle of 75° or 80° with the abdominal 
portion, and generally the animal has succeeded through the ac- 
tion of these muscles in restoring its head again to the glass. 
The muscle (OQ) on the back may possibly be attached to the 
muscle (N) and not to the thoracic segment. We have not suc- 
ceeded, in our dissections, in exposing these muscles in order to 
determine this point. 
b. Muscles of the organs appertaining to the several segments. 
1. Anterior Cephalic Segment.—In the following account, we 
shall in general describe only the muscles moving the basil 
joints of each of the legs. More minute particulars may be ob- 
tained by reference to the plates. 
~The muscles moving the cup, have not been satisfactorily de- 
termined. A slightly elevated line passes from each side with a 
curve into the membrane of this organ, which may be muscular ; 
if so, they act in flattening the cup preparatory to its attachment. 
The antenne have two extensors and one flexor. The two ex- 
tensors are inserted in a tendon, occupying the anterior margin of 
the base. They extend half way to the eyes; one (a, fig. 7 and 
fig. 1) above the flexor of the anterior cephalic segment, is 
page to the upper shell; the other, (a’, fig. 1,) much the small- 
under the same muscle, is attached below. The 
mtd (b, figs. 7 and 1,) is inserted near the outer part of the base, 
by means of a short tendon, and is attached near the base of the 
preceding muscles. 'These organs have but little motion, and are 
seldom observed in action. 
2. Posterior Cephalic Segment.—The elevators of the buccal 
mass are four short narrow muscles, inserted in the bony pro- 
cesses, g, (figs. 12or 17,) and attached to the teguments below, 
under the anterior extremity of the mouth ; the insertion of one is 
exactly posterior, and of the other, a little lateral, as is represented 
in fig. 17. By means of these muscles the buccal mass may be 
elevated to a right angle with the surrounding parts. On dying, 
the mouth is often left in this elevated position. A muscular 
band passes across the back part of the buccal mass and after 
