46 Records of the Indian Museum, [Voi.. XIII, 



merits ; 3rd thoracic sternite of female produced back- 

 wards as a large plate, the posterior edge of whichiis 

 free and emarginate [external antennular flagellum of 

 male with two clasping spines ; petasma without mem- 

 branous coupling folds, its internal lobe not expanded 

 proximally, the distal portion with bulbous termination 

 and with a large process on its outer side] ... japonicus, 



Kishinou3'e. 



In A. erythraeus , as already noted, the males are dimorphic, a 

 form with a short antennular peduncle, resembling that of the 

 female, being apparently by far the more abundant of the two. 

 In the other three species only one type of male — a form with the 

 ultimate segment of the peduncle greatly elongated — is known to 

 occur. 



The four species agree in the following particulars : — 



The rostrum is exceedingly short and projects very little 

 beyond the frontal margin of the carapace. It is, however, rather 

 strongly elevated and terminates in a sharp point, behind which are 

 two teeth, the foremost much the smallest. The anterior margin 

 is almost vertical and is sinuous or concave. 



The carapace is as long as, or rather longer than the first two 

 and a half abdominal somites; it bears conspicuous post-orbital 

 and hepatic spines. The cervical groove is obsolete and no trace 

 of it exists on the dorsum of the carapace. The upper limit of the 

 branchial region is defined posteriorly by a blunt longitudinal 

 ridge. 



The inner antennular flagellum is very long and in both sexes 

 shows the curious flexure described in detail by Kishinouye. 



The antennal scale is broadest at the base and is from 3"6 to 

 nearly 4 times as long as wide. The outer margin is rather strongly 

 convex and terminates in a small tooth that reaches almost to or 

 a trifle beyond the distal end of the lamella. 



The mandibular palp consists of three segments, the basal one 

 being exceedingly small and inconspicuous. The propodus of the 

 second maxillipedes is a trifle longer than the merus; the carpus is 

 from two-thirds to three quarters its length and is fully three times 

 the length of the dactylus. 



The third, fourth and fifth segments of the third maxillipedes 

 are more or less equal in length, while the fifth is from i"25 to i'4 

 times as long as the sixth. ^ 



The first three peraeopods increase successively in length, the 

 third pair reaching almost or quite as far as the third maxillipedes. 

 In the first pair the merus is about as long as the chela ; the latter 

 segment being from r*2 to i"4 times the length of the carpus. 

 In this pair of limbs, at the distal end of the carpus and at the 



l The proportionate lengths of the segments appear to show minor specific 

 characters. \n A. japonicus, A. erythraeus and A. tnsiilan's the third segment 

 is almost equal to, or a little longer than the fifth, whereas in A. indiciis the former 

 is decidedly shorter than the latter. In A. eiythraeus the third and fourth seg- 

 ments, taken together, are 1*3 times the length of the fifth and sixth, in A. 

 iiisidaris and A. japonicus i"2 times and in A. indiciis '94 to i"i times. 



