ON A NEW SPECIES OF SGLEROCHEILUS. 



407 



slightly damaged and no longer bear cirri. In the 18th and 

 19th chsetiferous segments the neuropodial cirrus is a short conical 

 process, *05-"08 mm. in length ; but those of the succeeding seg- 

 ments (fig. 6) rapidly increase in length, so that the cirri of the 

 33rd to 40th segments are finger-shaped and "25-'3 mm. long 

 (fig. 5). There are no notopodial cirri. 



A lateral sense-organ is present in each parapodium imme- 

 diately ventral to the base of the notopodium ; but as it is small, 

 and usually hidden in a depression, it can be seen satisfactorily 

 only in sections. The surface of the organ which bears the sense- 

 hairs is oval in outline, and its longer diameter is not more than 

 about 40/x. This area is sunk below the level of the surrounding 

 epidermis of the papilla on which the organ is situated. Ventral 

 to the papilla bearing the sense-organ is a larger eleva- 

 tion the epidermis of which is glandular (fig. 6). 



Clisetee. 



The first notopodium bears chsetae of three or 

 four different kinds, the relative positions and detailed 

 structure of which have been studied as far as has been 

 possible on the single intact notopodium available. 



(i) There is an anterior series of about ten almost 

 straight chsetse (text-fig. 1, A), approximately *5 mm. 

 long and 9-1 0/x in maximum diameter. Each of these 

 chsetse tapers rapidly in its distal fourth to a fine 

 point, and the preparations indicate that the tips of 

 these chsetae project little beyond the lips of the 

 chsetal sac. 



(ii) Close behind the chsetse just described is a 

 series of about fifteen stronger chsetse, each bent in a 

 characteristic manner (text-fig. 1, B). These chsetse 

 are '6— '65 mm. long, and their maximum diameter is 

 10-12/*. Each chseta tapers somewhat abruptly at its 

 free end, and, when unworn, has along both sides, 

 for a distance of '15 mm. behind the fine-pointed tip, 

 a narrow and very delicate lamina which readily 

 breaks up into a close-set series of minute, pointed 

 processes, so that this region of the chseta appears 

 to be finely spinous. It is possible that these chaetae 

 are really in two rows, an anterior row of about 



i B C D 



Text-fig. 1. — Chretae from the first noto- 

 podium of the specimen from Scotia Bay. 

 (x200.) 



