1896.] A. Alcock — Carcinological Fauna of India. 201 



the external maxillipeds is not much more than half the length of the 

 ischium measured along the inner edge : the 2nd segment of the exo- 

 gnath generally has the outer edge elegantly curved, but is not dilated 

 except a little at the base. 



The chelipeds though much more massive than the legs, and rather 

 more massive than those of Ilia, Arcania and their immediate allies, 

 are not nearly so massive as those of Leucosia, Philyra, etc. In some 

 species at any rate they vary much in length according to age and sex, 

 but they are seldom less, and are often more, than twice the length of the 

 carapace. The fingers are stout and vary in length, being sometimes 

 a little longer than, but in the adult males of one species only half 

 the length of, the hand. 



The abdomen of the male usually consists of 4 pieces, that of the 

 female of 5. 



The species of this genus are often difficult to discriminate owing to 

 the changes that they undergo in growth. The following key will, it 

 is believed, serve for the determination of adult forms. 



Key to the Indian species of Myra. 



I. Carapace broadly oval (longitudinally), with a 

 broad notch in the antero-lateral margin be- 

 tween the hepatic and branchial regions : — 



1. Side- wall of hepatic region forming a 

 distinct facet, behind which the lateral 

 margins of the carapace are defined 

 by a beaded line: spines of the post- 

 erior margin more or less acute : 

 fingers either shorter or hardly longer 

 than the hand : — 



i. Spines of the posterior margin 

 long and acute : carapace fine- 

 ly granular — the granules 

 hardly visible to the naked 

 eye: chelipeds slender (in the 

 adult male nearly thrice the 

 length of the carapace) : hand 

 long (in the adult male often 

 nearly twice the length of the 

 fingers, and about two-thirds 

 the length of the carapace) ... M. fugax. 

 ii. Spines of the posterior margin 

 short, the middle one acute, 

 J. ii. 26 



