17 



distal angles are more or less spout-like : if asymmetrical, one lobe is either larger 

 or longer than the other and both are split up into interleaved convoluted 

 lobules. 



The 3rd maxillipeds never exhibit secondary sexual characters in the male, 

 but the last pair of thoracic legs sometimes do. 



The branchial formula is : — 



Somite Poilobrancliiw Artluobrancliiw 



Total 



o cj: 



i. + I 



11 + i 



= oep.+ jy + i 



In addition, a small filamentous vestige of an anterior arthrobranch is 

 present on the penultimate thoracic somite in all the species I have examined, 

 which include, besides the Indian species, M. Joyncri, M. tcnelhs, M.Macleayi, 

 M. pMlippinensis, M. Bichtersi, and M. Bafei. 



Key to ilte Indian species of the genv>; Metapeneus. 



I. Telson without lateial marginal spinules : antero-lateral (antero-inferior) 

 angles of carapace without a spine : last paii' of thoracic legs without 

 exopodite, their merus, in the adult male, with a notch and spine at 

 base: — 



1. The rostrum in adult.f reaches nearly to, or beyond, the tip of 



the antennular peduncle : — 



i. Last pair of thoracic legs seldom reach to tip (usually- 



reach a little beyond middle) of antennal scale ... M. laonoceros. 



ii. Last pair of thoracic legs usually surpass (sometimes by 



a dactylus-length) the tip of the antennal scale ... M. affinis. 



iii. Last pair of thoracic legs fall considerably short of the 

 middle of the antennal scale, and often in the female 

 aie merelj' horn-capped stumps : inner antennular 

 flagellum the longer ... ... ... M. Dohsmii. 



2. The rostrum, in adults, sometimes just surpasses, sometimes 



hardly reaches, the eyes ; — 



i. Rostrum rarely leachcs middle of antennular peduncle : 

 last pair of thoracic legs i-eacli more than a dactylus- 

 length beyond the tip of the antennal scale ... M. hrevicornis. 

 ii. Eostrum rarely reaches middle of eye : last pair of 



thoracic legs do not reach tip of antennal scale ... M. Lysianassa. 



8 



