REPORT ON THE BRACHYURA. 
225 
middle of the carapace and originating on each side from the base of the posterior 
antero-lateral marginal tooth, from behind which, also, a granulated ridge extends 
along the postero-lateral margins of the carapace nearly to the postero-lateral angles, 
which are rounded, not spiniform, and not prominent. The orbit has two small incisions 
in its superior margin. The antero-lateral margins are shorter than the postero-lateral 
margins and are armed with four teeth ; of which the first, second, and fourth are pro- 
minent and spiniform, the third is almost obsolete on one side and exists on the other 
merely as a small tubercle. The front is rather prominent, about one-third the width of 
the carapace, and divided by a small median notch into two broad and slightly sinuated 
lobes, which are rounded at the lateral angles. The post-abdomen (in the female) is sub- 
triangulate, with the segments short, the fourth to the sixth apparently partly coalescent, 
the last segment rounded at the distal extremity. The antennules are transversely 
plicated ; the basal joint very large. The basal antennal joint is slender, and longer 
than the two following peduncular joints, but it is free and not conjoined with the infero- 
lateral process of the front, as in that genus ; the flagellum is somewhat elongated. The 
ischium of the exterior maxillipedes is longer than broad, with the inner margin 
convexly arcuated ; the merus is almost as long as broad (and much shorter than the 
ischium), it is subtruncated at its distal extremity, with the antero-external angle 
rounded and not at all prominent, and is scarcely at all emarginate at the antero- 
internal angle, where the next joint is articulated with it. No limbs remain attached to 
this specimen, but two ambulatory legs, which occurred in the same tube, and probably 
belong to it, are moderately elongated and very slender, with the joints smooth ; the 
dactylus styliform, nearly straight, elongated, slightly longer than the penultimate 
joint (see figs. 36, 3c). Colour (in spirit) whitish. 
Young $ . 
Lines. 
Millims. 
Length and breadth of carapace, 
5 
Length of ambulatory leg, about 
11-5 
Off the Bermudas, in 435 fathoms, in lat. 32° 21/ 30" N., long. 64° 35' 55" W., 
Station 33 (a young female). 
From all the described species of this genus, Geryon incertus is distinguished by 
the form of the front, and from the typical species of Bathynectes, Stimpson, not only by 
this character, but also by the structure of the basal antennal joint, which is free and 
not united with the lateral subfrontal process. 
Pilumnoplax, Stimpson. 
Pilumnoplax, Stimpson, Proc. Acad. Nat. Sci. Philad., p. 93, 1858. 
Carapace moderately transverse, and longitudinally slightly convex, or rather de- 
pressed ; the antero-lateral margins are very short, much shorter than the postero-lateral 
(ZOOL. CHALL. EXP. PART XLIX. — 1886.) Ccc 29 
