572 THE VOYAGE OF H.M.S. CHALLENGER. 



undoubtedly the same species, it is better to retain the specific name proposed by the 

 author of the older though less recognised synonym. 



Several specimens of this species were taken at the two localities given above. In 

 the case of those from Albany Island the depth is not recorded, but I presume they 

 were also taken in shallow water, and we may conclude that the species generally are 

 the inhabitants of shallow seas, or swim near the' surface of deeper waters. The ova 

 are large and not numerous. 



The branchial arrangement corresponds with that of Al/pheus excepting by the 

 absence of the mastigobranchial appendage to the second pair of gnathopoda and all the 

 pereiopoda, in which it closely corresponds with Synalpheus, as may be seen by the 

 following table : — 



Pleurobranchire, . . . 1 1 1 1 1 



Arthrobranchise, . . . 



Podobranchia?, . . . ... 1 



Mastigobranohioe, . . . 1 



h i k 1 m n o 



Synalpheus, n. gen. 



Carapace arcuate, dorsally elevated in the median line into a carina, and anteriorly 

 produced to a slender rostrum that is subequal with the length of the peduncle of the 

 first pair of antennae. Orbital margin projected over the ophthalmopoda and produced 

 to an anteriorly directed, prominent, sharp tooth ; fronto-lateral angle produced to a point. 



Ophthalmopoda concealed beneath the frontal margin of the carapace. 



First pair of antenna? furnished with a strong sharply pointed stylocerite ; upper 

 flagellum the shorter and divided into two branches, of which one is truncated. 



The second pair of antennae furnished with a strong tooth on the outer side of the 

 first and second joints of the peduncle ; scaphocerite sharply pointed, the styliform process 

 separated from the foliaceous plate for nearly half its length ; flagellum long and slender. 



The mandibles possess a stout molar jjrocess, a curved, sharply pointed, and almost 

 rudimentary psalistoma, and a small two-jointed synaphipod. 



The first pair of gnathopoda has the terminal joints enlarged and reflexed, the basis 

 furnished with a strong multiarticulate ecphysis, and the coxa bearing a short and broad 

 mastigobranchi a. 



The second pair of gnathopoda is five-jointed and pediform, the basis carries a 

 long uniarticulate ecphysis, and the coxa has a small podobranchial plume. 



The first pair of pereiopoda is slightly asymmetrical, having the carpos short, with 

 the upper and lower distal angles projecting, and the chelse large. The second pair is 

 long and slender, having the carpos multiarticulate, and the chela minute. The 

 posterior three pairs of pereiopoda terminate in a single pointed dactylos. 



