ORDER ISOPODA — CYMOTHOA. 47 



CYMOTHOA PRjEGUSTATOR. 



Onisau pragvstator. Latrobe, Am. Phil. Trans. Vol. 5, p. 77, PI. 1. 

 Cymothoi (jEga) id. Say, Jour. Acad. Nat. Sciences, Vol. 1, p. 395. 



Description. Body ovate, elongated, gradually tapering before from the sixth segment ; the 

 first four segments nearly equal in length ; the three following shorter. Head not tapering, 

 elongated, much longer than broad, transversely impressed near the tip, which is not narrowed. 

 Eyes conspicuous, oval, composed of punctures instead of granules. Antennae subequal, 

 hardly attaining the middle of the eyes. Last segment of the tail as long as the seven pre- 

 ceding ones united, gradually narrowed towards a point at the tip, with a perceptible longitu- 

 dinal line on the middle. Lateral styles membranaceous, alm'ost filiform, longer than the 

 peduncles, and much shorter than the segment to which they are attached. Feet gradually 

 longer to the seventh pair, which are much longer than the others. 



Length, 2-0. 



This species is very abundant in the mouth of the American Alewife (Alosa tyrannus of 

 the New-York Report). 



Cymothoa olivacea. 



PLATE X. FIC. 41, 41 a. Magnified. 



Description. Body oblong-oval, attenuated in front, smooth ; the transverse equal to half 

 the longitudinal diameter. Head pyramidal, rounded anteriorly ; first segment with three 

 emarginations, of which the central is most superficial. Bases of the antennae contiguous, of 

 eight articulations each, the anterior slightly longest. Eyes black, reticulated, conspicuous. 

 First segment broader than the following, and without an accessory lateral plate ; third and 

 fourth subequal) fifth, sixth and seventh broader, the last lunate. Segments of the tail 

 smooth, with no elevated medial line. Terminal segments subacutely ovate ; lateral appen- 

 dices longer than the terminal segment. Three last pairs of feet longest. 



Color. The three anterior segments olive-green ; all the others sparsely punctate with white, 

 and of a polished white on their posterior margins. Segments of the tail black. Abdomen 

 tumid, and of a rich olive-green or yellowish. 



Length, 0'75. 



I found numerous specimens of this species in the month of August in the harbor of New- 

 York, adhering to the gills and inside of the mouth of the Rhombus triacanthus, or Short- 

 finned Harvest-fish of this Report. 



