272 COLLECTIONS EKOM MELANESIA. 



defined by very distinct sulci, and the whole of its upper surface, 

 except near the posterior margin, very uneven ; the front is deeply 

 concave in the middle line, and its median interantennulary portion 

 much deflcxed, spinulose, the spinules of unequal length ; its lateral 

 margin armed with about seven spinules, and the protogastric lobes 

 also spinulose ; the peduncles of the antennae are without spinules. 

 The merus-joint of the outer maxillipedcs fits into a deep notch in 

 the anterior margin of the preceding joint, and is itself excavated 

 at its distal end. The single chelipede present in the unique ex- 

 ample before me has a spinulose lobe or tooth at the distal end of 

 the inner margin of the arm ; the wrist and palm are flattened on 

 the upper surfece, which is armed with tubercles arranged in longi- 

 tudinal series, the tubercles themselves for the most part minutely 

 spinulose ; the inner margin of the wrist is armed with three or 

 four spines at its base, and beyond with smaller spinules ; the 

 posterior margin is armed with about seven spines ; there are two 

 spines at the distal end of the inner margin of the palm., and its 

 outer margin is spinulose and pubescent ; the fingers meet closely 

 along their inner margins, which are entire, and their outer mar- 

 gins are spinulose. The first pair of ambulatory legs have the ante- 

 rior margins of the merus, carpus, and propus armed with a few 

 distant spinules, which are almost wholly absent from the same 

 joints in the following legs. Colour whitish. The single specimen 

 examined is a female : the carapace measures nearly 3 lines (6 mil- 

 lim.) in length and 2k (5 millim.) in breadth ; the chelipede, when 

 extended as far as its conformation will allow, about 5 lines (11 

 millim.). 



The single specimen was obtained at Port Molle, between tide- 

 marks (No. 103), with Petrolisthes japonicus. The description given 

 above will show that our specimen differs from Mr. Haswell's type 

 in the more uneven carapace with more numerous lateral marginal 

 spinules, non-pubescent posterior margin of the wrist of the cheli-« 

 pede, and in having two spines (not mentioned by Mr. Haswell) at 

 the distal end of the anterior margin of the palm (see fig. c). 

 If distinct, I would propose to designate this species P. dorsalis. 

 It seems, upon the whole, to have more affinity with the genus 

 Petrolisthes than with PorceUana, on which account I refer it, 

 although with some hesitation, to that genus. 



16. Polyonyx obesulus. (Plate XXIX. fig. D.) 



PorceUana obesula, White, List Crust. Brit. Mus. p. 130 (1847), de- 

 script, nulla. 



I refer to this species, though somewhat doubtfully, a female 

 obtained from Port Denison, 4 fms. (No. 122), also one from Prince 

 of Wales Channel, 7 fms. (No. Hi9), one from West Island, 7 fms., 

 and one from Port Darwin, 12 fms. These examples resemble the 

 three specimens in tho P>ritish- Museum collection, and differ from 



