ISOPODS OF NORTH AMERICA. 583 



There is no chord of attaehinent. On the ventral side is a small 

 rounded opening, where the parasite was attached to the host. There 

 seems to he an outer Widl and an inner wall. The outer wall is prob- 

 ably- attached to the host around the circular openino-. The inner wall 

 is guarded b}^ three or four valves. Through the integument of the 

 imier wall can be secMi the eggs which completely till the body cavity. 

 It was found attached to the ventral side of the alxlomen of th(^ Isopod 

 Pdiicolm californienHis Richardson, belonging to the family Tanaidiv. 

 There are but two specimens, ))oth females, and no males were found. 

 The types are in the V. S. Nat. Museum, Cat. No. 32111, U.S.N.M. 



VI. ONISCOIDEA." 



Legs all ambulatory in character. Uropoda terminal, styliform, 

 composed of a peduncle and two branches, the branches being uniar- 

 ticulate. Pleopoda fitted for air breathing, the outin- operculai- plate 

 of the tirst two pairs and sometimes of all live pairs containing air 

 cavities or trachea\ In the male the inner plate of the second pair 

 and sometimes of the tirst pair is modified. Abdomen composed of 

 six well-defined segments. 



The first pair of antenna? are small, rudimentary, and inconspicuous; 

 the}' are never composed of more than three articles. 



Mandibles strong, without palps. First maxilhe have two mastica- 

 tory lobes. Second maxjlla^ with only a very slight indication of a 

 subdivision into lobes. 



Marsupial pouch in the female composed of four pairs of plates 

 issuing from the bases of the second, third, fourth, and fifth pairs 

 of legs. 



This superfamily includes all the terrestrial Isopods. 



ANALYTICAL KEY TO THE FAMILIES OP ONISCOIDEA. 



n. Inner antennfe with one to two articles. Pleopoda in four pairs; those of first 

 segment wanting; those of the second, third, fourth, and fifth segments have 

 a single branch, all branchial; the branch of the second segment, however, in 

 the male, is produced on the inside in a long, compressed stylet; uropoda form 



an inferior operculum Family XXIII. Tvlid,e 



a' . Inner antenme with three articles. Pleopoda in five pairs, all double branched. 



External branch of all five pairs opercular in character. Internal branch 



branchial, in the male, however, of the first and second pairs sexual; uropoda 



not forming an operculum. 



h. First maxilhe with inner lobe furnished with from five to fifteen plumose 



processes Family XXIV. Eibelid.e 



//. First maxilla^ with the inner lobe furnished at the tip with only two or three 

 plumose processes, 

 c. Buccal mass not very prominent below. First maxilla' have two plumose 

 setfe on the inner plate. Mandibles with molar expansion obsolete, with- 

 out any triturating surface, it being replaced by brushlike recurved sette. 



« For characters of family see Budde-Lund, Crustacea Isopoda Terrestria, 1885, and 

 Sars, Crustacea of Norway, II, 1899, pp. 153-154. 



