484 Howard Edwin Enders. 



bcMi-iiig ''eyes." The pair of dorsal longitudinal muscles common to 

 many of the annelids is lacking in Chsietopterus, but a pair of thick 

 longitudinal muscles is conspicuous over the middle region. Each of 

 the three foremost segments of this region bears a more or less shield- 

 shaped disc. The posterior region bears a pair of external lobes of 

 the parapodia which diminish progi'essively in size to the anal seg- 

 ment. 



The antenor region. — The anterior region is firmer, somewhat 

 more opaque and more muscular than the remaining regions of the 

 body. Through its transparent dorsal surface are seen the septa 

 which correspond in number with the nine conical dorsal rami on 

 each side of this region. Its outline is better described as a tall 

 trapezoid than as a parallelogram, as Laffuie does. I would also 

 differ from this author in regard to the dorsal and ventral surfaces, 

 which are convex. In cross-section this region is elliptical in outline. 

 (Fig. 15.) 



The mouth of the adult is at the forward end of the anterior region. 

 It is surrounded ventrally by a broad flattened lip which is continued 

 dorsalward on each side in the form of an auriculate appendage that 

 overlaps the base of the tentacle of the same side. On the whole it 

 forms a broad funnel which is incomplete on its dorsal side. The 

 mouth is bounded dorsally by a thickened edge whose anterior margin 

 may be a rectilinear line transverse to the axis of the worm, or it may 

 at times form an obtuse angle with the auriculate appendages of the 

 ventral lip. Its form is dependent upon the activity of the living 

 animal, and the form assumed in the preserved specimens does not 

 well represent it. 



A pair of slender conical tentacles is located on the dorsal side of 

 the mouth immediately back of the thickened dorsal lip. At the 

 lateral margin of the lip the dorsally-directed auriculate lobes of the 

 ventral lip of the buccal funnel cover the base of each tentacle. They 

 bear a groove on their inner margin which is covered with a ciliated 

 epithelium as Laffuie says. In Spiochsetopterus the tentacles are as 

 long as the body of the worm and the ciliated grooves function as 

 important accessory feeding organs. 



The nine setigerous appendages are conical structures arranged at 

 the lateral margin of the anterior region, "\\nien they are extended 



