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



specific importance. The chelae are unequal, and although the larger has a resemblance 

 to that of Alpheus, yet it approaches to the more normal character of that appendage 

 in other genera, rather than to the oblique and distorted form that is frequently found 

 in Aljyheus. 



Family Hippolytida 



The genera in this family comprise those in which the carapace is produced to an 

 important rostrum, in which the first pair of pereiopoda is chelate and moderately 

 robust; the second pair slender with the carpos multiarticulate, and the posterior three 

 pairs of pereiopoda simple. 



It contains several genera, of which those represented in the Challenger collection 

 are briefly defined below : — 



Platybema, n. gen. 



Eostrum laterally compressed, deep. 

 Mandible without synaphipod or psalistoma. 

 First pereiopod chelate ; carpos excavate. 

 Second pereiopod chelate ; carpos Inarticulate. 



Latreutes, Stimpson. 



Eostrum laterally compressed, deep, serrate. 

 Mandible without synaphipod or psalistoma. 

 First pereiopod chelate ; carpos excavate. 

 Second pereiopod chelate ; carpos triarticulate. 



Hippolyte, Leach. 



Carapace with a supraorbital and an antennal tooth. Eostrum slender, toothed. 



Mandible without synaphipod, and with psalistoma. 



First pereiopod chelate ; carpos distally excavate. 



Second pereiopod chelate ; carpos triarticulate. 



Branchiae five in number ; mastigobranchiae four, rudimentary. 



Spirontocaris, n. gen. 



Carapace carinated, with two supraorbital and an antennal tooth. Eostrum 



deep, serrate. 

 Mandible with a rudimentary biarticulate synaphipod, and with a rudimentary 



psalistoma. 



