141 



but, unlike what is the case in that genus, the mandibles are provided with dis- 

 tinct, though rather small palps. The peculiar fornicate character of the posterior 

 division of the body has given rise both to the generic and specific names. 



Aspidaraehna clypeata 1 ), G-. 0. Sars. 



(PI. LXII.) 



Ilyarachna clypeata, G. 0. Sars, Nye Dybvandscrustaceer fra Lofoten. Chr. Vid. Selsk. Forhdl. 



1869, p. 168. 



Specific Characters. — Body scarcely more than twice as long as it is broad, 

 and generally much curved. Cephalon very broad in proportion to its length, frontal 

 edge evenly concaved, lateral parts obliquely expanded. The first 4 segments of meso- 

 some short and distinctly excavated transversally, with the anterior edge considerably 

 elevated and perfectly smooth, lateral parts acutely produced. The 3 posterior seg- 

 ments of mesosome very large and evenly convex above, forming together a shield-like 

 plate advancing in front over the adjoining part of the anterior division. Caudal seg- 

 ment triangular, scarcely as long as it is broad at the base, tip obtusely pointed. 

 Superior antennas with the basal joint very large, inner corner considerably pro- 

 duced, and armed with 2 long S23ines ; flagellum in female short, 3-articulate, in 

 male very much elongated, and divided into numerous short articulations clothed 

 with delicate sensory filaments. Inferior antenna? nearly twice as long as the 

 body, the 2 outer joints of the peduncle armed inside with slender spines, fia- 

 gellum about the length of the peduncle. The 4 anterior pairs of legs scarcely 

 different in their structure from those in the 2 preceding genera, except that the 3rd 

 and 4th pairs are very much shorter, not nearly attaining the length of the body, 

 and having the ischial joint the longest. Carpal joint of the 2 anterior pairs of 

 natatory legs strongly expanded, broadly cordiform in outline, and densely fringed 

 with plumose sette, propodal joint much shorter and oblong fusiform. Last pair 

 of legs, as in the 2 preceding genera, much more slender than the 2 preceding 

 ones. Uropoda with the basal part oblong oval and densely fringed with plumose 

 setas, outer ramus very small, though well defined. Colour whitish. Length of 

 adult female 4 mm. 



Remarks. — This is the only as yet known species of the genus, and may 

 easily be recognized by the short and compact body, and the peculiar fornicate 

 character of the posterior segments of the mesosome. 



') The generic name Aspidonotus given in the plate has been changed in the above 

 manner, because that name has been previously used in Zoology. 



