of legs, or the gnathopoda, into strong clieliform organs, a character not found in 

 any other Isopoda, and somewhat recalling the higher Crustacea, crabs and 

 lobsters. It is indeed from this character that the name of the group, chelifera, 

 proposed by the author, has been derived. Another very anomalous feature is 

 the complete fusion of the chephalon and the 1st segment of the mesosome, to form 

 a kind of carapace, and the localisation of the respiration to that part, instead 

 of, as in other Isopoda, to the metasome. In connection therewith is also the 

 more anterior situation of the heart in the present forms. The group contains 

 2 distinct families, Apseudidce and Tanaidce, both represented in the fauna 

 of Norway. 



Fam. 1. Apseudidae. 



Body more or less elongated, tapering behind, and subdepressed in front, 

 with the cephalosome rather broad and carinated laterally. Free segments of 

 mesosome very sharply marked off, and exhibiting at the insertions of the legs, 

 distinct, though small coxal plates. Metasome very narrow r , composed of 6 well- 

 defined segments. Eyes well-developed or rudimentary, being placed on distinctly 

 defined lobes at the outer corners of the frontal margin. Superior antenna? is- 

 suing far apart, just beneath the ocular lobes, and consisting of a 3 articulate 

 peduncle and 2 unequal filiform flagella. Inferior antennae much smaller than 

 the superior, and sometimes having at the end of the peduncle a small squaini- 

 form appendage. Mandibles rather strong, each with a well-developed molar expansion 

 and a triarticulate palp. Anterior maxilla? with 2 masticatory lobes, palp biarticulate 

 and terminating in a number of slender seta? ; posterior ones normally developed, 

 though rather small. Epignath of maxillipeds rather large, forming a broad 

 vaulted plate, terminating in a digitiform point. The 2 anterior pairs of legs unlike 

 the others, and provided at the base with a small biarticulate exopodite; 1st pair 

 distinctly cheliform and much instricted at the base, with the ischial joint obsolete; 

 2nd pair very powerful, fossorial in character, the outer joints being complanated 

 and edged with strong spines. Pleopoda well developed and having the rami 

 tipped with long natatory seta?. Uropoda biramous, rami filiform, multiarticulate, 

 the inner one much the longer. Incubatory pouch normal. 



Remarks. — This family is well distinguished from that of the Tanaidce 

 by the gradually tapering, and slightly depressed body, the greater development of the 

 cephalosome, the peculiar structure of the antenna? and of the 2nd pair of legs, 

 and the presence of a rudimentary exopodite at the base of the 2 anterior pairs 



