654 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



but the exopod is turned sidewise and appressed so close to the margin 

 of the basal apron that the latter overlaps it somewhat. This brings 

 the tip of the exopod over onto the endopod, so that the two appear 

 close together. The fourth legs are small and weak, three-jointed with 

 four spines; the first and third joints are about the same length, the 

 second joint is only one-third as long. 



The spine at the tip of the second joint is long, slender, and perfectly 

 straight; of the three at the tip of the third joint the inner one is very 

 short and rudimentary; the outer one is about the same length as that 

 on the second joint, and like it slender and straight. The middle claw 

 is much larger, nearly as long as the joint itself and strongly curved. 



Fifth legs as already stated. 



Total length 4 mm. Length of carapace 2.7 mm. ; width of the same 

 2.5 mm.; length of genital segment 1 mm.; length of abdomen 0.4 

 mm.; length of egg strings 3.5 mm. 



Color a light }^ellowish brown without pigment spots. 



{centrodonti, the specific name of its host.) 



Male. — Carapace as in the female, but proportionally much larger 

 (as 7 to 2); not narrowed as much anteriorly. Frontal plate larger 

 and wider and lunules larger. The median posterior lobe is not quite 

 as large proportionally and is slightly rounded along the posterior 

 margin instead of being emarginate. 



Free segment short and almost concealed beneath the carapace and 

 the genital segment. It is proportionally much wider than in the 

 female, and from tip to tip of the lateral plates is five-sevenths as wide 

 as the genital segment. 



The latter is narrower than in the female, but is of the same shape. 

 The fifth legs show plainly at the tips of the posterior lobes. Abdomen 

 relatively larger than in the female, with anal laminae almost as large 

 as itself. The abdomen proper does not reach to the tips of the pos- 

 terior lobes of the genital segment, but the anal laminae project well 

 beyond them (fig. 344). 



Of the appendages there is no increase in the size of the second 

 antennae, as is usual, but there is enough increase in the second maxil- 

 lipeds to more than compensate for this. Instead of the weak and 

 puny appendages found in the female, the male carries a pair of enor- 

 mous second maxillipeds. 



• The basal joint is swollen until it is fully as wide as long, and is 

 armed on the inner margin with two large protuberances or papillae, 

 into the sinus between which the tip of the terminal claw fits snugly. 

 This basal joint is supplied with very powerful muscles, particularly 

 the one which closes the terminal claw. The latter is three-quarters 

 as long as the basal joint and stout. 



The first maxillae are also very much enlarged, and are bent into a 

 sickle shape, with a slightly enlarged base. 



