produced^). Sergentes prehensilis Nobili (1906) from lat. i4°57'N., long. 5i°io'E. cannot be 

 S. prehensilis Bate or S. bisulcatus Wood-Mason ; whether is may be S. phorciis Faxon is 

 very uncertain. 



Whether S. mollis Smith from the North Atlantic is only a synonym to S. japotiicus 

 Bate cannot be settled with absolute certainty before the petasma of a male from the Japanese 

 seas has been studied; Bate's types in the British Museum are females. At present I am apt 

 to maintain my earlier opinion that .S'. mollis Smith is a synonym to 5. japoniacs Bate. 



S. ruSro-guiiatus Wood-Mason (1891) is probably impossible to determine with any 

 certainty from the description in the literature. An adult specimen received from the Museum 

 in Calcutta is an adult male of 5. cornicuhim Kr.. But from the "Siboga" I have a number 

 of specimens of a closely allied form, 6*. semimultts n. sp., which can only be separated from 

 5. cornicuhim Kr. by the structure of the petasma. As I do not know whether 5. seminudtis 

 is also to be found in the Bay of Bengal, the Andaman Sea or the Arabian Sea, it is impossible 

 to decide whether under the name 5. rubro-gicttahis A. Alcock has only referred specimens 

 of 5. corniculum Kr. or besides some belonging to S. seminudus n. sp. 



Diagnoses of the two Groups. 



Group I: Third maxillipeds at most but little longer, sometimes shorter 

 than third pair of legs; it first joint rarely, the second- fourth joints never 

 obviously incrassated in proportion to the joints in third legs, its two 

 distal joints with numerous bristles along both margins. 



Grotip II: Third maxillipeds considerably or much longer than third pair 

 of legs, its four proximal joints considerably or (generally) very 

 much incrassated or partially almost inflated in proportion to the 

 joints in third legs, its two distal joints with a lesser number of bristles, most of 

 them or all small or minute, or totally naked along the one margin, the sixth joint 

 with a number of spines very different in length along the other margin, and a feebler 

 armature may also be found on the fifth joint. 



Conspectus of the Species of Group I. 



Only adult and subadult specimens are taken into consideration. 

 A. On the exopod of the uropods the ciliated part occupies considerably less than half of the 

 exterior margin. 



a. The two distal joints of the antennular peduncles slender; third joint as long as or 

 longer than the inner margin of the second. Supra-ocular and hepatic spines well 

 developed. 



l) S. prehensilis Nakazawa and Terao (Zool. Mag. Vol. XXVII, n" 329) must be quite different from S. prehensilis Bate, as 

 pars media of the petasma according to their figure (kindly copied for me by Dr. W. T. Calman) differs extremely from that in .S. prehen- 

 silis Bate and every other species of the genus seen by me. 



