214 



Memoirs of the Indian Museum. 



[Vol. V, 



The chelipedes in the adult male are one and a half times the length of the 

 carapace, a little shorter in females and young males — about one and a third times. 

 Except for the under surface of the chela the entire chelipede is covered with minute 

 close-set granules similar to those on the carapace. The upper surface of the merus 

 bears three rather obscure rows of small tubercles and the granules on the outer 

 margin of the palm are rather larger than elsewhere. The palm is about one and 

 three quarter times as long as broad ; the fingers are about as long as the palm and 

 are grooved and provided with small teeth ; when closed, a small proximal gap 

 remains between them. The dactylus of the last leg is about one and a half times 

 as long as the propodus. 



In the male the marginal portions of the sternum are finely granulate and 

 deeply pitted. There is a huge longitudinal ridge, abruptly declivous posteriorly, at 

 the base of each chelipede and, in fully adult individuals, there is a very large tubercle 

 on either side of the abdomen opposite the bases of the first walking legs (text-fig. 2). 



The abdomen of the male consists of three 

 movable pieces and is not granulate. The first 

 segment is acutely produced on either side and, 

 though it appears distinct, is in reality fused to the 

 succeeding piece. The penultimate portion is about 

 one and a third times as long as broad; at its base 

 it is sharply angulate on either side and broader 

 than the distal end of the preceding piece. The 

 ultimate segment is a little less than twice as long 

 as broad. The abdomen of the female is very 

 coarsely and deeply pitted, the ultimate segment 

 being a trifle longer than broad. 



The largest specimen, a female, is I3'5 mm. in 

 length. It is only in males measuring 12-5 mm. 

 and upwards that the characteristic sternal tubercles are developed. 



In its produced and narrow front, provided with a median tooth that projects 

 beyond the endostome, P. alcocki resembles Pseudophilyra rather than Philyra ; but 

 it agrees with the latter genus in the shape of the buccal cavern and of the outer 

 maxillipedes. Laurie, in discussing the characters of P. adamsi 1 has already com- 

 mented on the features in which certain species of Philyra resemble Pseudophilyra ; 

 there is little doubt that the present species, along with that which Laurie examined, 

 may correctly be referred to the platycheira section of the former genus. 



Philyra alcocki seems to find its nearest ally in P. olivacea, Rathbun 2 , a species 

 described from Lern Ngob in the Gulf of Siam, but differs from that form in numerous 

 details. In P. alcocki, for instance, (i) the carapace is noticeably broader in propor- 

 tion to its length ; (ii) its surface is not so conspicuously granulate ; (iii) the rows of 



1 Laurie, Rep. Pearl Oyster Fisheries, Ceylon, V, p. 364 (1906). 



2 Rathbun, Proc. Biol. Soc. Washington, XXII, p. 108 (1909) and Danske Vidensk. Selsk. Sknfter 

 (7), Naturvid. og math., V, p. 312, pi. ii, fig. 17, text-fig. 4 (1910). 



Fig. 2. — Philyra alcocki, sp. nov. 



Carapace of large male, ventral view. 



