1896.] A. Alcock — Carcinolog leal Fauna of India. 165 



Among the genera known to me by autopsy, however, two extremes 

 of form are plainly recognizable, and I propose to use these two ex- 

 tremes as the bases of two natural alliances or sub-families. 



The first alliance is typified by Leucosia and Philyra^ the second by 

 Ilia and Iphiculus. 



In Leucosia and Philyra the merus of the external maxillipeds is 

 as long as the ischium measured along the inner border ; the fingers are 

 stout and compressed, taper gradually from a broad base, and are 

 usually shorter than the hand ; the hand is stout, compressed, and if 

 anything a little broader at its distal end than at its base ; and when 

 the specimen is laid face downwards on the table, with the chelipeds 

 resting on the table in a semi-fl^exed position, the fingers open and close 

 in a horizontal plane. 



In Ilia and Iphiculus , on the other hand, the meras of the external 

 maxillipeds is only half the length of the ischium measured along the 

 inner border ; the fingers are slender and of almost the same diameter 

 from the base to near the hook-like tip, and are very much longer than 

 the hand ; the hand is either subglobular, or tapering-cylindrical with 

 a swollen base ; and when the specimen is placed in the position above 

 desciibed, the fingers open and close in either a vertical or obliqne plane, 

 and in Iphic2ilus the dactylus can, without any breakage or unnatural 

 dislocation of parts, be moved through an arc of about 120°. 



Speaking only of the genera known to me by autopsy, the followino-, 

 though they differ a good deal from jLe?«cosz a in the characters under 

 consideration, doTiot differ nearly so much as they do from Ilia : — Pseu- 

 dophilyra, Myra, Parilia, Bandallia, Ehalia, Ntirsia, Merocryptus, Onycho- 

 morpha. Tlos and Oreophorus also, although their fingers move in a 

 nearly vertical plane, yet in other respects show no close affinities with 

 the Ilia type, but rather, through Nursia, with the Leucosia type ; and 

 Actseomorpha goes with Oreophorus. 



On the other hand, the following Indian genera belong to the Ilia 

 alliance : — Myrodes, Iphiculus, Nursilia, Arcania. Ixa also, although its 

 fingers are much shorter than the hand, clearly in other respects 

 belongs to this alliaTice. 



I would define these two subfamilies as follows : — 



1. Subfamily Leucosiinse. Merus of external maxillipeds more, 

 often much more, than half the length of the ischium measured along 

 the inner border : fingers stout, gradually narrowing from base to tip, 

 seldom much longer, commonly shorter, and often very much shorter 

 than the hand, either opening in a horizontal plane or if in a vertical 

 plane then the immobile finger is markedly more massive than the 

 dactjlus, the tip of the dactylus hardly ever movable through an arc 



