46 NEW-YORK FAUNA — CRUSTACEA. 
GENUS CYMOTHOA.. Fabricius. Lamarck. 
Body oval, oblong, subconvex, of six transverse segments. Tail of six segments, narrower 
than those of the body; the last segment largest, and having on each side a fin composed 
of two compressed scales. Feet fourteen, with stout nails; the coxe large, and resembling 
an accessory lateral articulation of the thoracic segments. ‘Two sessile eyes. Antenne 
four, setaceous, rather short ; the external slightly longest. 
Oss. This large genus has been erected by recent writers into a family composed of ten 
genera. We retain at present the original genus Cymothoa. The species are all parasitic, 
being attached to the mouths and gills of fishes. 
CYMOTHOA TRILOBA. 
PLATE X. FIG. 40. 
(STATE COLLECTION.) 
Description. Body elongate, elliptic ; the transverse more than half the longitudinal dia- 
meter of the body. First segment as broad on the medial dorsal line as the two following 
segments united ; it is emarginate on its anterior edge, to correspond with the trilobed divi- 
sion of the head : its accessory lateral plate united so closely as to form a continuity with the 
segment ; last segment lunate. Surface of al! the segments smooth, with irregular opaque 
marks ; the posterior margins opaque, polished. Head ovate in front, where it is slightly 
reflected downward, trilobed behind ; the middle lobe largest. Eyesinconspicuous. Anterior 
pair of antenne shortest. Segments of the tail gradually decreasing in breadth, with an obso- 
lete elevation on the medial line; terminal segment equal in length to the five preceding, 
subquadrate, narrowed and rounded behind, with a membranous tip, and a faint elevated 
transverse line on the upper surface. Lateral appendices about equal in length to the terminal 
segment; the external lamella longest. 
Length, 1:0. Extreme breadth, 0-6. 
This species has many characters in common with the C. wnpressa of Say ; but (indepen- 
dent of marked differences) his doubts whether it might not be synonimous with C. ichthyola, 
Latr., induces me to believe that he had in view a species entirely distinct from that described 
above. It differs from C. oculata, Say, by the conspicuous eyes and the size of the middle 
lobe of the head in the latter species. I am unacquainted with the C. trigonocephala of 
Leach, except by a brief notice in the Dictionnaire des Sciences Naturelles. 
This species is very common on various fishes. The specimen here described was detached 
from the surface of the Common American Codfish. 
