46 

 JPlatyniaia tvijville-thomsoiii, Miers. 



Platymaia u-yville-thomsoni, Miers, 'Challenger' Brachyura, p. 13, pi. ii. fig. 1. 



Platymaia u-yville-thomsoni, "Wood-Mason and Alcock, Ann. Mag. Nat. Hist., March, 1891, p. 258, and Jlaj". 

 1891, p. 401 : Alcock, J. A. S. B., Vol. LXIV. pt. 2, 1895, p. 181 : Illustrationa of the Zoolosry of the Investi- 

 gator, Crnst. pi. xvi. (adolt male natural size). 



Carapace transversely sub-circular vritli the cervical grove well defined: 

 its surface ranging from spinate (in the young) to nearly smooth (in old adults). 

 The rostrum, which is so short as not to break beyond the general outline, 

 consists of three stout spines of equal size, the middle one being the horizon- 

 tally projecting interantennulary spine. 



The hepatic region of the carapace bears (in the adult) a nearly vertically 

 disposed row of three spines, against the upper one of which the eye is retrac- 

 tile. 



The eyestalks are short, and the eyes large and oval. The antennte are 

 about one-third the length of the carapace, and are plainly \'isible, in almost the 

 whole of their extent, from above : the joints of the peduncle are short slender 

 and cylindrical, the basal joint being perfectly free. 



The external maxillipeds have the meropodite narrow (about half the 

 breadth of the ischiopodite) and gi^'ing attachment to the coarse palp at the 

 summit : both meropodite and ischiopodite are spiny. 



The chelipeds vary considerably according to sex : in both sexes they are 

 spiny up to the base of the fingers ; but whereas in the female and young male 

 they are much slenderer than any of the legs and are not longer than the cara- 

 pace, in the adult male they are from two to three times the length of the cara- 

 pace and are much stouter than any of the legs — especially as regards the palm, 

 which is swollen and club-shaped. 



The legs are long and slender, with the joints thin and compressed, the 

 propodites being blade-like. The 1st pair, which are from 3f (female) to 5^ 

 (male) times the length of the carapace, are remarkable for their propodite and 

 dactylus, the front edge of which bears a double comb of enormous spines, the 

 posterior edge also being spinulate : both edges of the merus and carpus also 

 are distantly spinulate. The 2nd and 3rd pairs have the front edge of the merus 

 distantly spinulate, and they, as well as the 4th pair, have the front edge of the 

 razor-hke merus closely fringed with long stiff hairs. 



The abdomen in both sexes is seven-jointed, the abdominal terga, like the 

 thoracic sterna, bearing a few spines or tubercles. The epimeral plates corres- 

 ponding to the third and fourth trunk legs are also spinate. 

 Andaman Sea, 130— i05 fathoms. 



In very young specimens (carapace less than half an inch in diameter) the 

 whole carapace is closely and sharply spiny. 



