CRUSTACEA. 53 
The anterior or upper labia is small and tubereuliform, 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 subprismatic, 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 upon 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 oe of six articles, including the basal, 
already alluded to. The second article is the second also in size; then the fourth Gipep! ae 
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 clean. cylindrical, tapering, ae 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 setze and moveable upon 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 sete. 
Inwardly and laterally they are provided in the female with wuditnentary three-jointed, egg- 
bearing legs. A subpentagonal thin piece, as sixth segment, terminates that region, irene 
on either side caudal paddles composed of a basal poh eee alan 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 sete 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 setee, more thickly set, and more developed upon the tarsal article. 
The body and tail are bluish yellow above, yellowish beneath. The legs are reddish and 
bluish, and the antenne reddish. 
Specimens were collected in the upper affluents of the Rio de Maypu, 2,000 feet above the 
level of the sea, near Santiago. 
8 
