ISOPODS OF NORTH AMERICA. 583 



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

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

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

 ably attached to the host around the circular opening. The inner wall 

 is guarded by three or four valves. Through the integument of the 

 inner wall can be seen the eggs which completely fill the body cavity. 

 It was found attached to the ventral side of the abdomen of the Isopod 

 r<incoliL8 californiensis Richardson, belonging to the family Tanaidx. 

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

 The types are in the U. 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 outer opercular plate 

 of the first two pairs and sometimes of all five pairs containing air 

 cavities or tracheae. In the male the inner plate of the second pair 

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

 six well-defined segments. 



The first pair of antennae are small, rudimentaiy, and inconspicuous; 

 they are never composed of more than three articles. 



Mandibles strong, without palps. First maxilla? have two mastica- 

 tory lobes. Second maxillae 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 OF ONISCOIDEA. 



a. Inner antennae 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. TYLID.E 



a' '. Inner antenna; 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. 



b. First maxillae with inner lobe furnished with from five to fifteen plumose 



processes Family XXIV. EI - BELID.K 



V . First maxillae with the inner lobe furnished at the tip with only two or three 



plumose processes. 



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

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

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



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

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



