580 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



The second antennae are much longer than in the female and three- 

 jointed; the basal joint is broad and oblong and is attached to the ven- 

 tral surface by its long posterior side. At its inner extremity it turns 

 upward to receive the following joint. The second joint is broad and 

 well rounded; its entire inner and ventral surface is covered by a 

 swollen pad formed of chitin ridges overlapping one another like 

 clapboards on a house, giving an admirable rasp-like surface for the 

 prevention of slipping (tig. 123). 



The terminal joint is obliquely articulated with this second joint and 

 is much smaller and shorter. It terminates in two stout claws, widely 

 divergent and quite strongly curved. 



There is a slender seta on the outer margin and another on the inner 

 surface near the base. 



The second maxillipeds are much enlarged, the basal joint being 

 swollen with a width considerably more than half its length (fig. 124). 



The terminal claw is less than half the length of the basal joint, but 

 is stout and furnished with powerful muscles. Its tip shuts into a 

 socket formed at the base of a large spine on the ventral surface of 

 the basal joint, affording a strong grip. Between this spine and the 

 base of the terminal claw there is another shorter and smaller spine 

 with an acuminate tip. This shuts in past the side of the terminal 

 claw when the latter is closed and thus strengthens the hold. The 

 other appendages are like those in the female. 



This species is one in which the males are larger than the females, as 

 can be seen in the following measurements: 



Total length 13-20 mm; length of carapace 7.5-12 mm.; width of 

 same 7.4-11.5 mm. ; length of genital segment 2.5-4 mm.; length of 

 abdomen 2.5-4 mm. 



Chalimus, later stages. — Carapace narrow ovate, much longer than 

 wide, about 0.64 of the entire length, contracted considerably through 

 the frontal plates. Posterior sinuses narrow and slit-like; median lobe 

 projecting nearly its entire length behind the lateral lobes (fig. 115). 



Posterior portion of the body very narrow and of nearly the same 

 diameter throughout. Free segment of good length and well rounded 

 at the sides; genital segment also well rounded, with the fifth legs 

 showing on either side near the posterior end. 



Abdomen a little narrower, but with well-rounded sides; anal laminas 

 large and broad. 



The lunules appear early upon the frontal plates and are large and 

 semicircular in outline. The eyes are small, highly colored, and placed 

 relatively much farther back of the frontal margin than in the adult. 

 The appendages are nearly the same as in the adult. 



Chalimns, early stages. — Carapace, a still narrower ovate, becoming 

 sharply pointed in front. This latter is due almost entirety to the 

 frontal plates, whose width is more than one-third the length of the 



