426 CRUSTACEA ENovember, 



Cabinet of the Academy. 



Body composed of seven segments, tail of two; seg- 

 ments of the body with the lateral processes, very con- 

 vex, lobated, first segment shortest; Aefltf/ transverse, oval, 

 imequal on the disk, an impressed transverse line behind, 

 sinuate anterior edge, and impressed w^ith a longitudinal 

 abreviated line; antennce filiform, rather distant, interme- 

 diate ones short, exteriores with the terminal joint rather 

 more than half as long as the preceding one; eyes very- 

 prominent, hemispherical, placed in the middle of the 

 lateral margin; tail narrower than the body, first segment 

 trilobated, middle lobe much the largest, convex, uid f'.ate 

 segment rather longer than the three preceding ones con- 

 junctly, subtriangular, very convex on the disk, margin 

 near the base depressed and channelled, tip depressed, 

 acute; feet rather long, armed with curved, acute nails. 



Length one fourth of an inch. 



Found with the preceding species, is remarkable by 

 the lobate appearance of the lateral processes. Of the I. 

 triloba 2i new genus might be formed with the greatest 

 propriety, as the description will evince. 



Genus hSEl^UJS. Geoff, 



Tail one large segment; cmidal appendices exserted, 

 bifid, inserted near the middle of the hind margin; ex- 

 terior branchial valves rounded, attached by the base; 

 tarsi simple; eyes minute; antenna four, setaceous, the 

 last segment many -jointed. 



