1S96.] A. Alcock — Carcinological 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-flexed position, the fingers opeu and close 

 in a horizontal plane. 



In Ilia and Iphiculus, on the other hand, the merus 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 

 described, the fingers open and close in either a vertical or oblique plane, 

 and in Iphiculus 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 following-, 

 though they differ a good deal from Leucosia in the characters under 

 consideration, do not differ nearly so much as they do from Ilia : — Pseu- 

 dophilyra, Myra, Parilia, Bandallia, Ebalia, Nursia, 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 alliance. 



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 

 dactylus, the tip of the dactylus hardly ever movable through an aic 



