G72 MR. E. J. MIERS ON THE 



as are clmracterized by a depressed carapace and excavated ptery- 

 gostomian and subhepatic regions, this excavation forming, when 

 the chelipedes are retracted, passages to the efferent branchial 

 apertures. 



This excavation, however, varies not only in direction and 

 depth, but is traceable in species not otherwise very nearly allied ; 

 and I would suggest the following as more convenient subgeneric 

 divisions : — 



Subgenus 1. Lambrus. Carapace subrhomboidal, not produced 

 at its postero-lateral angles over the bases of the ambulatory legs. 

 Anterior legs greatly elongated and spinose (usually more than 

 three times as long as the carapace) . Type Lanibrus cremilatus, 

 Sauss. 



Subgenus 2. PARTnEwoPOiDES, liters. Carapace subtriangular 

 with the posterior margin nearly straight, and produced at the 

 postero-lateral angles over the bases of the ambulatory legs. An- 

 terior legs rarely spinose and of moderate length (rarely exceed- 

 ing 2| times the length of the carapace). Type PartJienopoides 

 massena (Eoux). 



This subgenus includes those Lamhri which approach Parthe- 

 oiope in the lesser development of the anterior legs, and includes 

 several species which have been described as members of that 

 genus. 



DESCRIPTION OF THE PLATES. 

 Plate XII. 

 Fig. 1. Btmorhynchus rodratus (Linn.). Front of the cephalo thorax, dorsal 

 view, showing the laterally projecting eyes and the absence of orbits ; 

 X nearly 3 diameters. 



2. Inferior view of the same, showing the slender basal antennal joint 



and large epistome ; X nearly 3 diam. 



3. Oregonia hirta, Dana. Front of the cephalothorax, showing the pro- 



jecting rim which covers the base of the ocular peduncle and the 

 prominent postocular spine ; X 3 diam. 



4. Inferior view of the same, showing the form of the narrow basal an- 



tennal joint and of the epistome ; X 3 diam. 



5. Xenocarcinus tuberculatus, White. Inferior view of the front of the 



cephalothorax, showing the immobile eyes and the form of the basal 

 antennal joint ; X 3 diam. 



6. Acanthonyx lunulatus, Eisso. Inferior view of the front of the cepha- 



lothorax, showing the form of the basal antennal joint and the partial 

 concealment of the eyes beneath the prominent prseociilar spine; X 3 

 diam. 



