420 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



Abdomen small, one third the length of the carapace, nearly as wide 

 as long-, and ovate. Anal sinus reaching- just to the center of the abdo- 

 men; posterior lobes triangular, slightly divergent and very wide at 

 the base, almost obliterating the anal sinus. Anal papillae minute and 

 basal, almost concealed between the bases of the posterior lobes. 



First antennie stout, the claw twice the length of the rest of the 

 basal joint and stouth' curved; the two terminal joints minute and 

 scarcely reaching the tip of the claw. 



At the base of these antennai is a pair of stout spines, one on either 

 side of the mid-line and some distance from it; each is strongly curved 

 outward. Second antennee small, no longer than the first, the joints 

 diminishing regularly in size, the last three armed with bristles in the 

 usual manner. 



Mouth-tube stout and somewhat swollen at the tip; mouth opening 

 subterminal and very similar to that in A. versicolor. Mandibles 

 slender and not strongly curved, the teeth on the convex side large 

 with bluntly rounded tips; those on the concave side slender and 

 needle-like, longest at the point of the mandible, then growing rapidly 

 smaller, and entirely disappearing at about the center of the side. 



First maxillipeds large, the sucking disks being. fully one-fifth the 

 width of the carapace. This margin is supported in the usual manner 

 by rods, which, instead of being made up of segments, as in most 

 species, appear to be continuous and perfectly homogeneous. 



Second maxillipeds stout and of the usual pattern, the basal joint 

 armed with a triangular plate, which is broad and projects far behind 

 the appendage. Its posterior margin is cut into three wide and blunt 

 teeth, or, rather, laminte, evenly rounded and very similar to those 

 on A. catostonti Nearly the entire ventral surface of the appendage 

 is covered with spines and papilla?; the terminal claws are short and 

 blunt. 



Swimming legs of the usual pattern, the fourth pair with large 

 boot-shaped posterior lobes, the toes of which project beyond the 

 lateral margins of the abdomen. 



The male is similar to the female, with the exception of the sex dif- 

 ferentiations. The posterior lobes of the carapace are longer, as 

 already stated, and just reach the anterior margin of the abdomen. 

 The latter is relatively longer than in the female and narrower; the 

 anal sinus does not extend to the center, and the tips of the posterior 

 lobes are more bluntly rounded. The testes are long and narrow and 

 situated close to the mid-line on either side. 



The accessory sexual organs are in the form of broad laminate 

 appendages, very prominent even in a superficial view. The two rami 

 of the fourth legs are much widened, particularly the proximal joint 

 of the endopod, whose posterior border is flattened into a broad lam- 

 ina several times as wide as the terminal joint. At its base where it 



