Boone, Annelida, Cruises of "Alva" 81 



Tlie prostomium has only the distal margin visible dorsally. 

 This margin is comparatively straight. The median tentacle arises 

 from a broad base, which is produced a little in advance of its 

 distinct lateral portion, each of which supports a long, slender, 

 ctenidium, three-fourths as long as the median tentacle and con- 

 sisting of a proximal portion one-half as long, divided into twelve 

 constricted sections, not true joints, the distal third being slen- 

 derer, composed of about six articles. The median tentacle, which 

 is subequal in length to the lateral tentacles, has its distal portion 

 distinctly dilated and the tip marked by constrictions, indicating 

 three rudimentary rounded lobes distally. The bases of the lateral 

 pair of tentacles are each dorso-lateral in position, the lateral ten- 

 tacle being very flexible, constricted into twelve to fourteen sec- 

 tions, as is the median tentacle, and having the tip enlarged and 

 distally bifid into two rounded lobes. The base is constricted and 

 supports on its outer side a long, slender ctenidium which is nearly 

 as long as the tentacle. 



The eyes are four in number, small ; the anterior pair being 

 situated on the lateral prominences, and the posterior pair near 

 the posterior margin, nearly concealed by the jugal fold. 



Ventrad the prostomium presents a median concavity from 

 which the proboscis extrudes and ectoventrad the prostomium is 

 divided into two swollen lobes. 



The proboscis is conical, moderately stout, nearly as long as 

 the dorsal tentacle and is covered on the distal half with "papillae" 

 or rough setae, set in transverse bands, those of the ventral por- 

 tion appear to be coarsest. 



The peristomium closely and evenly margins the prostomium. 

 The first, second, third and part of the fourth segments are 

 coalesced, or partially so, forming a somewhat subrectangular, 

 dilated area. 



Twelve pairs of elytra are normal to this species, the five 

 pairs which are present, arise from somites two, four, six, eight 

 and ten, while those broken off, are represented by cirrophores 

 on somites twelve, fourteen, sixteen, eighteen, twenty, twenty- 

 two, and twenty-four. The elytra are very nearly subcircular, 

 with the free anterior margin widely rounded, projecting ante- 

 riorly over the tentacles for half their length and semiconcealing 

 them. On its outer side, adjacent to the parapodia, the elytra 

 is bent, but not incised ; posteriorly the round free margin over- 



