Report on the zoological collections made in the Indo-Pacific Ocean ...

238 'COLLECTIONS FROM MELANESIA.than its greatest vertical depth, which is at the articulation withthe mobile finger, smooth and polished externally, its upper marginnot carinated, its inner surface with a dense patch of hair ; thelower margin of the immobile fiuger is in a straight line with thelower margin of the palm, its upper or inner margin is denticulatedand has a strong tooth or lobe in the middle ; the inner margin ofthe mobile finger has a smaller tooth near its base ; the fingers,when closed, meet only toward their apices, having an hiatus betweenthem, which is hollowed out into a deep, nearly semicircularcavity at the base of the immobile finger ; this cavity is marginedwith hairs. The ambulatory legs are slender, somewhat compressed,and the margins somewhat thinly clothed with hair. Colour, inspirit, brownish. Length of carapace nearly 3 lines (6 millim,),breadth 3| lines (somewhat over 7 millim.) ; length of chelipedeabout Sg lines (over 11 millim.).The single specimen (a male) was obtained at Port Jackson,5-7 fms. (No. 104).In the relatively narrow and quadrate carapace this species maybe compared to such forms as Macrojjlithalnms pacificus, Dana *,to which species apparently belong specimens recently received fromTimor Laut (//. 0. Forbes), Macrophtlialmus hicarinatus. Heller f,and M. qaadratus, A. Milne-Edwards %.M. jyacificus and M. bicarinatus difi^er in their narrower front,&c. ; M. quadratus has but two lateral marginal teeth, and no lobeor tooth on the inner margin of the immobile finger. Macroplvthalmussetoaus, an Australian species very briefly characterized byMilne- Edwards §, has, I suppose, a wider carapace. Specimensprovisionally referred to this species in the British-Museum collectionare certainly veiy distinct from our new species.Macrophtludmus latifrons, Haswell ||,from Port Phillip, has thecarapace finely granulated, the immobile finger of the chelipedesdeflexed, &c.In many of its characters our species approaches Euplax {Choenostoma)boscii and E. crassimanus, Stimpson, in both of which thereare but two teeth on the lateral margins of the carapace. InHemiplax Mrtipes, Heller, not to mention other distinctions, thefingers are only minutely denticulated on their inner margins. Inthe absence of catalogues or systematic lists of the species, it is withgreat hesitation that I venture to describe this as a new form among80 many nearly allied species.83. Euplax (Chsenostoma) boscii (Audouin).A small male is in the collection from Port MoUe (No. 95).This example in its coloration and all other cliaracteristics coin-* U.S. Exploring Expedition, Crust, xiii. p. 314, pi. six. fig. 4 (1852).t Reise der Novara, Crust, p. 36. pi. iv. fig. 2 (18(J5).+ Nouv. Archiv. Mus. Hist. Nat. ix. p. 280, pi. xii. fig. 6 (1873).§ Ann. Sci. Nat. ser. 3, Zool. xviii. p. 159 (1852).Catalogue,II p. 90 (1882).