1904.] NATURAL SCIEXCES OF PHILADELPHIA, 495 



very irregular and inconstant in different individuals, but always dimin- 

 ishing in size and distinctness toward the posterior middle line and 

 often grouped in pairs. The lateral lobes, which reach forward to 

 the palpode, are considerably more elevated and bear five or six larger, 

 more prominent, rounded teeth. The mouth is a conspicuous opening 

 bounded behind by a transverse fold and laterally by distinct thickened 

 lobes. Behind it is a distinct peristomial half-ring rendered more 

 conspicuous by contraction. 



There are nineteen setigerous somites, the first seven thick-walled 

 and largely glandular, the first six strongly biannulate with the anterior 

 ring larger and setigerous. This region is usually slightly depressed 

 with each of the first six somites about as long as wide, but the unian- 

 nular seventh only ec[ualling the larger anterior ring of the others. 

 Behind VIII the somites increase gradually in length and become some- 

 what narrower to XVI, which is three times as long as wide; XVIII, 

 XIX and XX become successively shorter. From the eighth to the 

 nineteenth inclusive the parapodia are posterior in position, and the 

 more anterior are situated on complete glandular zones which soon be- 

 come incomplete and restricted to the lateral faces of the somites. 

 Distinct constrictions occur at the in termetameric furrows which are 

 rendered much more conspicuous by the prominent tori preceding them. 

 The surface of all somites is more or less annularly furrowed and bears 

 numerous small glandular and sensory papillae. The last somite (XXI) 

 bears no setse and is smooth and uniannulated. Caudally it enlarges and 

 passes gradually into the anal funnel, dorsad of which the anus is situ- 

 ated behind a somewhat wrinkled anterior fold. The anal funnel con- 

 sists of two parts, the ventral funnel proper, the cavity of which reaches 

 to the anterior end of the anal segment while the margin is even and 

 not at all flaring, and the dorsal platform, which arises within the dorsal 

 part of the ventral funnel and spreads in a flat, broad petaloid form 

 vertically behind the anus. The margins of both parts are slightly 

 irregular, but entirely without lobes or processes. 



On the anterior somites the parapodia are strictly lateral, on the 

 posterior ventro-lateral and more prominent. Somite II bears setae 

 alone. III to XX both dorsal setse and ventral uncini. The setae are 

 of three forms which, however, vary and intergrade. The several 

 kinds arise in more or less distinct fascicles, but spread in such a man- 

 ner that they appear at the surface in pairs or triplets composed of one 

 of each kind; thus on II they form a fan-shaped figure of about 25 

 pairs, on III about 15, on IV 12, on V 10 and a more irregular arrange- 

 ment in triples on the abdominal segments. Slender capillary wingless 



