NO. 3556 PORTUNID CRABS—STEPHENSON AND REES 97 
Chelipeds: Equally sized, very spinous, and hirsute. Arm bearing 
five spines on anterior border, none on posterior border, and one on 
ventral surface just behind wrist articulation. Wrist with inner 
spine very well developed, with three usual outer spines and with 
additional spine on upper surface. Inner and outer carinae of wrist 
well developed. Hand with upper surface bearing four particularly 
well-developed spines (apart from one at wrist articulation), but 
corresponding inner and outer carinae not recognizable. Outer sur- 
face of hand peculiarly folded just behind articulation of movable 
finger, and bearing on lower surface a very conspicuous carina com- 
posed of large regularly arranged granules, and terminating just 
before beginning of immovable finger in a forwardly directed spine. 
Lower border of outer surface composed of a carina of regularly ar- 
ranged granules, continuing along immovable finger. Inner surface 
of hand with coarsely granular subcentral carina. Under surface of 
hand granular and hairy. Fingers short, sharp, and_ strongly 
carinated. 
Walking legs: Unique in possessing a spine on ventrodistal border 
of merus of each leg. Dorsodistal border of carpus of first and 
second legs bearing similar, but less obvious spine. Dactyls of all 
three legs with sharp spinous tips. 
Fifth leg: Merus twice as long as broad and with spine on distal 
border particularly well developed, and another smaller spine on 
posterodistal angle. Dactyl sharp tipped. 
Discussion.—This specimen is either a most unusual Thalamita or 
alternatively should be referred to a new genus. It resembles the 
species of the genus Thalamonyx A. Milne Edwards, 1873, in possessing 
inclined anterolateral borders and a protruding front. Stephenson 
and Hudson (1957, pp. 326-327) have already shown that inclined 
anterolateral borders are possessed by some species of Thalamita and 
have suggested that Thalamonyzx should disappear into the synonymy 
of Thalamita (see also Stephenson and Campbell, 1960, p. 107). 
It is uniquely spinose on the merus of all walking legs (hence the 
specific name), on the carpus of the first two legs, on the under surface 
of the arm of the chelipeds, and on the outer surface of the hand of the 
chelipeds. In addition the dactyls of the walking and swimming legs 
are more spinous than usual, and the spine on the posterior border of 
the merus of the fifth leg is particularly well developed. Presumably 
these are adaptations for its ectocommensal mode of life and are in the 
nature of special additions to the basic body plan of a typical Thala- 
mita, rather than marked diversions from it. Apart from the spinous 
dactyls of the fifth legs, none of these adaptations are comparable with 
those in the genus Caphyra, which has presumably evolved separately 
and farther from Thalamita-like ancestors. 
