1905.] NATURAL SCIENCES OF PHILADELPHIA. 857 



and deeply folded longitudinally. The prostomial membrane forms a 

 prominent horseshoe-shaped fold or upper lip above the mouth, while 

 its tentacular fold is narrower and bears the tentacles in a nearly contin- 

 uous band around its entire margin. On its posterior face are right and 

 left groups of numerous, rather large, conspicuous, nearly black eyes 

 arranged for the most part in one row and separated by a narrow 

 dorsal space. 



The large mouth is coverd by the upper lip, the inner surface of 

 which bears a prominent grooved longitudinal ridge on each side of the 

 middle line, and is bounded below by a thick slightly bilobed pad within 

 the membranous anterior margin of the peristomium. 



As far as about XX the anterior somites are short, the length not ex- 

 ceeding one-fourth or one-fifth of the width ; those following are about 

 two-thirds as long as wide, none is distinctly annulated, but all are rough 

 and furrowed both above and below. The first four segments are 

 glandular all round ; the others have the thick glandular layer confined 

 to the ventral half, but covering their entire length and extending to 

 and including the setse tufts. At about XVIII the glands disappear 

 from the anterior one-third of the ventral surface also. The dorsum is 

 thin-walled but rugous and constitutes less than one-third of the cir- 

 cumference. 



Two pairs of branchiae are developed and are situated dorso-laterally 

 on II and III. The first consists of six and the second of three detached 

 and independent filaments about as long as the diameter of the body; 

 the area of attachment of the former extending over the entire length of 

 the second segment, while that of the latter is limited to the anterior 

 margin of the same dorso-lateral level of the third segment. 



Setae tufts begin on III and continue on all succeeding segments 

 throughout the length of the specimen. All are small but prominent, 

 little flattened and oblique, and are retractile within pits in the gland- 

 ular layer of the skin. Throughout they are situated at a high level. 

 Uncinigerous tori begin at V. They are all short, never exceeding 

 one-sixth of the ventral interspace, and are separated from the corre- 

 sponding setse tufts by nearly their length. Posteriorly they grow 

 smaller but more prominent. Like the setigerous tubercles they are 

 situated in thin-walled, sunken spots within the glandular area. 



The first seta tuft includes about twelve rather short, acute, slightly 

 curved setae with very narrow wings. In others the setae (fig. 16) are 

 more numerous, longer and more strongly curved. Still farther back 

 in the posterior region they again become fewer. The uncini are 

 arranged in a single series on all somites and number from 40 to 60. 



