306 REPORT OP COMMISSIONER OF FISH AND FISHERIES. 



This genus may be recognized among our Onlscidce by the rounded 

 head without lobes, and the conspicuously narrowed pleon. Only a 

 single species is as yet known from New England. 



PMloscia vittata Say. 



Philosda vittata Say, Jour. Acad. Nat. Sci., vol. i, p. 429, 1818. 

 Dekay, Zool. New York, Crust., p. 50, 1844. 

 White, List Crust. Brit. Mus., p. 99, 1847. 



Harger, This Report, part i, p. 569 (275), 1874 ; Proc. U. S. Nat. Mus., 

 1879, vol. ii, p. 157, 1879. 



PLATE I, FIG. 1. 



This species may be recognized, among our terrestrial Isopoda, by the 

 absence of the usual autero-lateral processes on the head, in front of 

 the eyes, and by the sudden contraction of the body at the base of the 

 abdomen or pleon. 



Body oval, smooth; about twice as long as broad; head nearly 

 twice as broad as long; eyes large, occupying the antero-lateral regions 

 of the head. The antenuulae are minute and concealed from above. An- 

 tennae minutely hirsute, especially on the last three, or flagellar, seg- 

 ments, inserted below the inner margin of the eyes ; first segment short ; 

 second about twice as long as the first ; third equal in length to the sec- 

 ond, clavate; fourth longer cylindrical; fifth longest, slender, cylindrical, 

 straight; flagelluin slender, three-jointed, longer than the fifth or last 

 peduncular segment; first flagellar segment about one-half longer than 

 the second ; third longer than the second, tapering, tipped with a short 

 transparent filament. 



The first thoracic segment is longer than the following ones, which are 

 of about equal length. The anterior angles of the first thoracic segment 

 are somewhat produced at the sides around the head ; the posterior angles 

 are broadly rounded. The second and third segments have their pos- 

 terior angles less broadly rounded, but not at all produced backward. 

 In the fourth segment this angle is scarcely produced, but in the fifth, 

 and still more in the sixth and seventh, it becomes produced and acute. 

 The legs increase in size and length from the first to the seventh pair, 

 and are well armed with spines, especially upon the inferior surfaces of 

 the meral, carpal, and propodal segments. The spines on the latter seg- 

 ment are, however, much smaller than those on the merus and carpus. 



The pleon is at the base about two-thirds as wide as the seventh thoracic 

 segment. In the first two segments of the pleon the coxae, or lateral lamel- 

 lae, are short, small, and nearly concealed by the seventh thoracic segment, 

 but in the third, fourth, and fifth segments they are evident and acute but 

 not large. The sixth segment is acute but not prolonged behind, and ex- 

 tends beyond the end of the basal segment of the uropod, which is broad 

 and bears the two rami nearly on the same transverse line. The outer ra- 

 mus, seen from above, is narrowly and obliquely lanceolate in outline, 

 tapering to the tip, and surpasses by less than half its length the more 

 slender, styliform inner rainus. The uropods, the legs and antennae, and 

 the segments of the pleon, along their margin, are very minutely hirsute. 



