REPORT ON THE CRUSTACEA MACRURA. 583 



propodos articulating with the carpos at the inferior angle only, giving the appendage 

 the appearance of partial dislocation. This is a character that was first noticed by 

 Milne-Edwards in the genus Caridina, and has been overlooked by Stimpson and de 

 Haan in their descriptions of Platybema. The type of Latreutes is distinguishable 

 from that of Platybema by the form of the rostrum, which is orbicular in one and 

 cultriform in the other, but according to my observations the two genera approach each 

 other even in this character, and the only anatomical features that appear to distinguish 

 one from the other, exist in the first pair of gnathopoda and in the second pair 

 of pereiopoda, and these can be better appreciated by comparing the figures than from 

 a complicated description. 



Latreutes ensiferus (Milne-Edwards) (PI. CIV. fig. 1). 



Hippohjte ensiferus, Milne-Edwards, Hist. Nat. Crust., t. ii. p. 374. 



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



Body slender and but slightly sinuous at the third somite of the pleon. Carapace 

 dorsally rounded, armed with a small tooth on the gastric region. Eostrum nearly as 

 long as the carapace, vertically broad, of extreme tenuity, slightly curved upwards on 

 the upper surface towards the apex ; extremity serrate, lower margin smooth and 

 curved downwards in the middle. Antero-lateral angle of the carapace serrate with 

 five or six small teeth. 



Ophthalmopoda of medium size. 



Second pair of gnathopoda (fig. If) having the penultimate joint short and fringed 

 with spines on the distal margin, the terminal joint long and fringed with spines on 

 the inner margin, and the antepenultimate as long as the two preceding, which circum- 

 stance de Haan considers of sufficient importance to be regarded as of generic value. 

 This joint is armed on the distal half of the outer margin with stiff movable spines, 

 the basis carries a short ecphysis, and the coxa a podobranchial plume. 



The first pair of pereiopoda (fig. Ik) is short and robust, the meros is excavate 

 to receive the carpos, and the carpos is excavate to receive the posterior upper lobe of 

 the propodos ; the upper distal angle projects over the propodos and is tipped with a 

 fasciculus of long hairs. The propodos articulates with the carpos at the lower angle 

 and is broader at this extremity than at the dactyloid ; the dactylos is broad and 

 spoon-shaped, and corresponds in length with the pollex. The second pair of pereiopoda 

 (fig. lZ) is longer than the first, slender, feeble, and minutely chelate ; the carpos 

 is triarticulate, the central articulus being the longest, and together the three are 

 longer than the propodos, of which the fingers are nearly half the length. The other 

 pereiopoda are moderately long and robust, the propodos is long and the dactylos 

 short ; the former is furnished with long spines on the under surface, and the dactylos 



