REPORT ON THE CRUSTACEA MACRURA. 581 



The pleopoda are biramose, the second pair (fig. 2q) has the branches foliaceous, the 

 outer tapering, the inner broad, discoidal, and fringed with plumose hairs, and on the 

 inner margin is a single short stylamblys tipped with a few cincinnuli. On the inner 

 side of the basal joint there are numerous long hairs to which the ova are attached. 



Latreutes, Stimpson. 

 Latreutes, Stimpson, Proc. Acad. Nat. Sci. Philad., January 1860, p. 96. 



Eesembles Platyhema. Rostrum elongate, being more than half the length of 

 the carapace, laterally compressed and deep. 



First pair of antennae subequal in length to the rostrum. 



Second pair carrying an acutely pointed scaphocerite. 



Mandible without synaphipod or psalistoma, the molar process alone being present, 

 and curved at nearly a right angle with the apophysis. 



The first pair of gnathopoda is seven-jointed and carries a mastigobranchia and an 

 ecphysis. 



The second pair is five-jointed, robust and rigid, carries a small podobranchial 

 plume and a short ecphysis, and terminates in an obtuse extremity. 



The first pair of pereiopoda is short and robust and terminates in strong and simple 

 chelae ; the propodos articulates with the carpos at the inferior angle, the upper portion 

 falling into an excavation in the distal margin of the carpos ; the carpos also articulates 

 with the meros at the infero-distal extremity, and when extended falls into a similar 

 excavation. The second pair of pereiopoda is slender and chelate, the carpos being 

 inarticulate. The posterior three pairs of pereiopoda are slender and terminate in a 

 simple dactylos. 



The pleopoda are biramose, the branches being subequal. The telson tapers to a 

 point. 



This diagnosis differs in some points from that given by Stimpson. That 

 author says that the carapace is armed with a dorsal median tooth ; this is the case 

 in his typical species, Latreutes ensiferus, while in Latreutes unidentatus and in 

 Latreutes dorsalis there are two ; but on the other hand Latreutes planus has none, 

 and with this exception the resemblance of this species to Latreutes unidentatus 

 is very close. 



The chief distinction of this genus from Platyhema appears to me to exist in 

 the number of articulations in the carpos of the second pair of pereiopoda. In the 

 typical species, Latreutes ensiferus, of which I have had a great number for examination, 

 the carpos is triarticulate, and in Platyhemas according to my experience of 

 Platyhema rugosus, the carpos is only Particulate. The species of the two genera 



