162 THE VOYAGE OF H.M.S. CHALLENGER. 



terminates in an unequal-fingered chela ; the dactylos is long, but the pollex or terminal 

 process of the propodos is scarcely half the length of the dactylos. 



The mastigobranchiag are absent from all the pereiopoda, and the podobranchiae are 

 attached to scale-like stalks; in other respects the several branchial plumes correspond 

 with those of Stereomastis sithmi, and agree with the tabulation given for that species. 



The first pair of pleopoda in our specimen, which is that of a male, is loug, slender, 

 delicate, and spatuliform, but not so broad as in most male forms of other species ; the 

 second and following pairs are biramose and foliaceous. The inner branch of the second 

 pair carries two stylamblydes, one long and straight, terminating in an enlarged point, 

 the other short and rudimentary; in all the other pairs the smaller or rudimentary 

 stylamblys is absent. 



Observations. — This species is one of considerable interest, since it offers a very great 

 difference in the structure of some of its parts from others found associated with it 

 in the same locality. It is usual for the male to carry two stylamblydes attached to 

 the inner ramus of the second pair of pleopoda, but although in this species we have two, 

 one of them is almost rudimentary, and all the other pleopoda have only one. 



The first pair of pleopoda is very narrow, and its spatuliform character is much 

 diminished ; it is only by close observation it can be determined to be that of a male 

 animal, a circumstance that is corroborated by an examination of the foramen on the 

 coxa of the posterior pair of pereiopoda. 



The second pair of gnathopoda has no mastigobranchia but only the rudimentary 

 bulb of one. In all the pereiopoda the mastigobranchia is wanting as a free appendage, 

 while from the squamous and ridged stalk the podobranchial plume is developed ; but 

 this, though sufficiently large in the third pair of pereiopoda, is smaller than the 

 arthrobranchia. The condition of the branehiaB was such as to preclude a very close 

 examination, the more so as the specimen is unique, and it was desirable not to injure 

 it more than was absolutely necessary. I have no doubt that the general arrangement of 

 the several branchial plumes corresponds with the table as shown in Stereomastis suhmi. 



It was taken in the same locality as Pentacheles gracilis and Pentacheles euthrix, 

 about 70 miles south-west of the Fiji Islands, at a depth of about three-quarters of 

 a mile, and associated with Penseus and Ojilophorus. 



Willemossia, Grote. 



Willerncesia, Grote, Nature, vol. viii. p. 485, October 1873. 



,, Sp. B., Ann. and Mag. Nat. Hist., ser. 5, vol. ii. p. 276, October 1878; Kep. Brit. 



Assoc, 1878. 

 Deidamia, Willemoes-Suhm, Notes from the " Challenger," Nature, vol. viii. p. 51, 1S73. 



Carapace depressed, armed on the frontal margin with a single rostral tooth projecting 

 obliquely upwards ; lateral margins subparallel, anteriorly and posteriorly converging, 



