252 Description of a Species of Caligus. 
These seven pairs appear to correspond to those of the first tho- 
racic ganglions in the macrural crustacea. ‘The remaining nerves 
pertain to the thoracic legs, and the abdominal portions of the 
body.* 
The outer pair (1) belong to the anterior natatories. They 
continue parallel with the spinal cord till they reach the furcate 
on the venter; they then curve outward, exterior to the 
véritral muscles, give off three branches in succession from the 
outer side, to the muscles of the first natatory. Before entering 
the basal joints of these legs, they divide into three portions, 
which enter together; the inner branch is quite slender, and pass- 
es to the posterior movable seta, and the jointed appendage; the 
middle is distributed to the muscles of the basal joint; the outer 
branch gives a slender nerve to the apex of the basal joint, and 
then passes to the two following joints, dividing as it enters them. 
We refer for minuter details to figure 18, Plate 
This pair of nerves give off a slender branch near their origin, 
(r, fig. 20,) which passes to the attachments of the stomach. 
The next pair of nerves (m) are distributed to the second pair 
of —e ran diverge from the spinal cord—to which they 
—below fareate process, and soon give off a br 
* The apparent correspondence of these nerves, with those of the first thoracic 
OS in the paws sony ie together with the great similarity in the last two 
to those which ar dist#ibuted to the ponents pair of a in the 
t the designations hereto in speaking if eis organs 
of this segment of the body, in which we consider the three posterior pairs of ce- 
phalic legs as the anologues of the three pairs of maxillipeds i in the typical species. 
The only objection which can be urged to this view, arises from there then being 
but four pairs of thoracic legs. This objection will however be removed if we may 
consider the furcate bone on the venter, just anterior to the first pair of natatories, 
as the rudiment of the sternum of a fifth pair, which view is favored by its 
tion, and its resemblance to the sternums of the rece pairs. 
If this conclusion is correct, the twenty-one rings, the normal number consti- 
tuting the body, may be considered as distributed in the following manner 
The anterior cephalic segment, includes the second and third, as the frst —the 
ophthalmic—is wanting. The posterior cephalic segment, contains the following 
six, corresponding to the mandibles, (fourth,) and a pair of maxilla, (fifth,) in the 
mass; and the four pair of feet attached to this segment. The anterior 
thoracic segment will include the tenth, eleventh, twelfth and thirteenth rings; 
which the furcate te proc many the. two peire Salis natatory legs, and the apron, pertain. 
The posterior th ri The remaining seven Tings» 
the abdominal, constitute the terminal portions of the body; sos 
may however be wanting. 
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