EEPOET ON THE CEUSTACEA MACEUEA. 149 



The posterior pair of pereiopoda is smaller than either of the preceding, and terminates in 

 an unequal and imperfect chela, the pollex being shorter than the dactylos, and curved 

 in the same direction, so that the pollex seems to impinge posteriorly against the 

 dactylos. This pair supports no podobranchia or arthrobranchia; but a pleurobranchial 

 plume is attached to the inner wall of the chamber, and the whole may be tabulated as 

 follows : — 



Pleurobranchia?, . . .... 



Arthrobranehise, . . .... 



Podobrauchias, . . .... 



Mastigobrauchise, 



h 



The first pair of pleopoda in the female is small, slender, and uni-branched, whde 

 the four succeeding pahs are large and biramose, carrying on the inner side of the 

 inner branch a single stylamblys, fringed with a few plumose hairs on the approximate 

 side, and tipped with a bunch of cincinnuli. 



The rhipidura offers no distinctive variation from the same in allied genera. 



Observations. — This species was taken about one degree south-west of the Fiji 

 Islands, associated with Pentacheles euthrix and Stereomastis auriculata. 



Pentacheles euthrix, (Willemoes-Suhm, MS.) (PI. XVII.). 



Willemcesia euthrix, Willemoes-Suhm, MS. 



Pentacheles enthrix, Sp. B., Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 280, 1878. 



Margins of the carapace slightly convex ; antero-lateral angles slightly approximat- 

 ing, and somewhat abruptly turned upwards ; anterior division armed with eight teeth, 

 and defined from the central, which has four, and the posterior, which has twelve or 

 thirteen. The anterior margin has two rostral teeth, two small ones above the first pair 

 of antennae and one within the margin of the internal angle of the orbit. The median 

 longitudinal ridge is armed posterior to the two rostral teeth by two single and 

 one double and another single one before the cervical ridge, and behind it a double 

 and after a space another double, and on the anterior edge of the posterior margin three 

 stout teeth or cusps on each side. All of which may be formulated as — 



Marginal, ....... 8—4—13 



Dorsal crest, 2-1 -1 -2-1— 2-2-2 



On the pleon the carina is produced to a sharp tooth on all the somites anterior to 

 the fifth, where it is reduced to a strong cusp, and is almost lost on the sixth somite. 



The first pair of pereiopoda has the meros armed with two small teeth on the outer 

 margin near the base, and a small one near the distal external angle ; and in some 



