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

;CRXrSTACEA. 53742. Tetralia cavimanus, Heller.Seychelles, 4-12 fms. (No. 194), nine specimens ; Etoile Island,13 fms. (No. 191), five specimens.Specimens are in the British-Museum collection from Rodriguez{H. H. Slater) ; lied Sea, Gulf of Suez {11. MacAndrew) ; DaedalusShoal {Lt.-Col. Playfair) ; Tiji Islands, Ovalau, Totoya {H.M.8.^Herald''); and others without special locality. In some specimensthere is a very distinct transverse band of daiker colour on the frontin others it is scarcely, or not at all, discernible. The pit on theouter margin of the hand near the wrist, whereby Dr. Heller distinguishesthis species from T. glaherrima (Herbst), varies greatlyin depth : ordinarily, in well-grown and even in smaller examples,it is deep, well defined, and clothed with hair ; but in other rathersmall specimens it is so shallow as scarcely to be distinguishableand devoid of hairs. Ordinarily, in adult males, the lower finger ofthe larger chelipede is more or less strongly dentated on its innermargin, and there is scarcely any interspace between the fingerswhen closed ; but in two very dark-coloured males from theSeychelles, in the Alert ' ' collection, the fingers are scarcelydentated and are strongly arcuated, meeting only at the tips. Asimilar variation occurs in a male from the collection of H.M.S.' Herald,' which, on account of the entire absence of the palmarpit, is referred to T. c/laberrima.I think the T. heterodactyla of Heller is probably a mere varietyof T. cavimanus, to which species (if, indeed, it be distinct fromT. glaherrima) nearly all the specimens of this genus in the Museumcollection must be referred. Although several species of this genushave been described, of earlier date than T. cavimanus, by l)ana,Stimpson, and Lucas, by none of these authors, I believe, is anymention made of the subbasal pit on the palm of the chelipedewhich is so characteristic of T. cavimanus.pedes, I am not even sure whethei" it should be referred to the Cyclometopa orto the Catometopa. In most of its clmracters, however, it nearly resembles aspecies of Jrapcsia, differing mainly in the more elongated convex and regularlyhexagonal carapace and in the dactyli of the ambulatory legs. The carapaceis smooth and slightly but regularly convex ; the front is about half thegreatest width of the carapace, and is divided by three notches into four prominenttriangular teeth, the median notch being the deepest ; there is also a smallspinule or tooth at the inner supraocular angle, and a short spine at the widestpart of the carapace at the angle where the autero-lateral and postero-lateralmargins unite. The endostonie or palate has faintly indicated longitudinalridges. The postabdonien is shaped nearly as in Ira^jf^/a. As in 7V«^er/«, theinner and inferior margin of the orbit reaches to the front and excludes theantennte, and bears a strong spine; the basal peduncular joint of the antenna?is rather short, and the penultimate joint reaches to the frontal margin. Theouter maxillipedes present nothing remarkable, having a truncated merus-joint,and exognath reaching to its extero-distal angle. Of the legs only the third audfourth are present on each side ; tliese are rather longer and slenderer than inTrapesia, and the three terminal joints are somewhat hairy ; the dactyli arearmed on their inferior margin with about half-a-dozen spinules, which increasesuccessively in length. Colour (in spirit) yellowish white. Length of carapacenearly 4^ lines (9 iniilim.), breadth nearly 5 lines (10 millim.).