CRUSTACEA. 257 



The anterior or ttpj^er labia is small and tuberculiform, situated in a concavity of the episto- 

 ma concealed by a slight ridge. 



The anterior — pincers or claws-bearing— pair of legs is the stoutest and longest of the am- 

 bulatory appendages. The second, third, and fourth pairs are flattened; the second a little 

 longer than the third, and the third a little longer than the fourth. The fifth pair is very ex- 

 iguous, folded inwardly, and not used at all as an ambulatory organ. 



The first (basal) article in the anterior four pairs of legs is similar in shape and structure in 

 all ; preserving, however, their due proportions. 



In the first pair of legs the second article is su.bprismatic, short and stout^ larger than the 

 first article, angular anteriorly and inwardly, provided with a few rudimentary spines along its 

 inner edge. The third article (arm) is prismatic, tapering, posteriorly provided with a row of 

 small spines upon its edges, and subtubercular upon its anterior margin. The fourth article 

 (carpus) is short, subtriangular and stout, provided iipon its inner edge with a double series of 

 tubercular spines. The fifth article (hand) is subelliptically rounded exteriorly, flattened in- 

 wardly, and provided upon its inner margin with a flattened processus, subcrenated upon its 

 edge. The inferior claw, slightly curved inwardly, is concave upon its middle, and margined 

 with a series of transversally elongated and depressed tubercles disposed upon a double row 

 towards its base. The upper claw is elongated, subcylindrical, tapering, curved downwards, 

 thus forming an arch above the inferior one ; being similarly provided upon its margin with a 

 series of flattened, transversally-elongated tubercles, largest posteriorly. 



The second, third, and fourth pairs of legs are composed of six articles, including the basal, 

 already alluded to. The second article is the second also in size ; then the fourth (carpal), which 

 is slightly bent downwards; then the fifth; the third is the longest of all ; the sixth (tarsal), 

 about equal to the fifth in length, is very slender, cylindrical, tapering, and terminated by a 

 minute spine. 



The fifth and exiguous pair of legs, inserted, as stated above, upon the post-thoracic and 

 moveable segment, is composed first of a very small subglobose article, followed by four others 

 more elongated and slender, subequal, slightly diminishing in length from the base towards the 

 tip, which consists in a rudimentary claw concealed under a tuft of sette and moveable U]3on the 

 fifth article. 



The caudal region is shorter than the carapax ; bent upon its middle, and brought forward 

 beneath in close contact with the inferior surface of the body, the extreme margins of the caudal 

 paddle covering the posterior half of the sternal shield. It is composed of five segments, divided 

 into three lobes by a lateral undulating groove. The posterior four segments are angular, and 

 acute externally, while the anterior one is rounded ; all being margined with a series of setaa. 

 Inwardly and laterally they are provided in the female with rudimentary three-jointed, egg- 

 hearing legs. A subpentagonal thin piece, as sixth segment, terminates that region, having 

 on either side caudal paddles composed of a basal subtriangular piece inserted partly upon the 

 fifth segment, and directed forwards ; whilst on the latter are inserted, towards its external ex- 

 tremity, two subelliptical plates, margined with setse as well as the central piece, and directed 

 backwards and inwards. 



The main surface is minutely punctured ; the second, third, and fourth pairs of legs are pro- 

 vided with short and scattered set», more thickly set, and more developed ujjon the tarsal article. 



The body and tail are bluish yellow above, yellowish beneath. The legs are reddish and 

 bluish, and the antennee reddish. 



Specimens were collected in the upper affluents of the Kio de Maypu, 2,000 feet above the 

 level of the sea, near Santiago. 

 33* 



