i8 



Records of the Indian Museum. 



[Vol.. VII, 



little doubt that all are correctly referred to the species described 

 in the ' Challenger' Report. 



The resemblance of the species to the well-known Medi- 

 terranean form, A. foliacea (Risso), is very striking and Bouvier 

 in his account of the Peneidae collected by the Prince of Monaco 

 (1908, p. 56) was unable to determine the distinctions with any 

 degree of precision. On comparing the two species, however, 

 several characteristic differences may be observed. 



The rostrum in both sexes is shorter in A. rostfidentata than 

 in specimens of A. foliacea of larger size. In the single female 

 example of the former species, the rostrum trends more strongly 

 upwards towards the apex than in specimens of A. foliacea of 

 the same sex, while in male A. rostndentata it reaches only to 

 the end of the basal joint of the antennular peduncle and its 

 lateral carina is straight, or slightly concave ventrally, showing 

 no trace of the sinuosity seen in male A . foliacea. 



But perhaps the most important distinction is to be found 

 in the areolation of the carapace. The pterygostomian region 

 is much broader in proportion to its length in A. rostridentata 

 than in A . foliacea and the same is true of the branchial region, 

 though the differences in this case are not so well-marked. In 

 A . rostridentata the length of the pterygostomian region (measured 

 from the antero-lateral margin of the carapace to the postero- 

 dorsal end of the hepatic groove) does not exceed 2*5 times 

 its greatest breadth, while it is more than 3*5 times as long 

 as broad in A. foliacea {cf. figs. 5 and 6, pi. i). The ridge defining 

 the upper boundary of the branchial region is, moreover, slightly 

 less sinuous in the Indo-Pacific species. 



The specimens examined yield the following measurements 

 (in mm.) : — 



In other respects there appears to be an extremeh'^ close 

 resemblance between the two forms, but the dactyh of the 

 last two pairs of peraeopods, which, in the specimens of A. rostri- 

 dentata, are unfortunately broken off in all but two instances, 

 appear to be longer than in A. foliacea and measure more than 

 half the length of their respective propodites. The telson, also, 



