180 THE ANNELIDA POLYCHAETA. 



Odontosyllis Claparede. 



Beobacht. anat. entw. wirbell. thiere, 1863, p. 47; Malaquin, Recherches sur les syllidiens, 1893, p. 68. 

 ?Photocharis Ehrenberg, Abhand. K. akad. wiss. Berlin, 1834, p. 8. 



Odontosyllis atypica, sp. nov. 



Plate 21, fig. 3, 4; Plate 22, fig. 1-3. 



Epitokous Male. 



The body is colorless and translucent excepting the eyes and the anterior 

 region, consisting of the somites not bearing natatory setae, which is dark and 

 opaque from the contained sexual products. All setae colorless and trans- 

 parent. 



The type, which is incomplete caudally, is about 18 mm. long. Its greatest 

 width, exclusive of the parapodia, is 1.1 mm. ; inclusive of the parapodia 1.5 mm. ; 

 and to tips of natatory setae, 2.5 mm. In the anterior division there are thirty- 

 six somites, in the median forty-nine, and in the caudal (incomplete) twenty-six, 

 making a total of one hundred and eleven. The body is widest near the junction 

 of the anterior and median divisions, from where it narrows continuously caudad 

 to the narrow caudal division and also cephalad to the prostomium. The venter 

 is throughout but weakly arched. The dorsum in the anterior region is strongly 

 convexly arched, but toward the caudal region becomes lower and but weakly 

 arched like the venter. 



The prostomium is small, bent downward, much wider than long, with 

 the anterior margin incurved between the eyes where the tentacles are attached. 

 There are the usual two pairs of eyes occupying the sides of the prostomium. 

 On each side the upper and more posterior one is elongate in the anteroposterior 

 direction, broadly subfusiform in outline, and with the axis directed dorsoectad. 

 The anterior eye lies below the anterior end of the other one and extends a little 

 farther forward; it is decidedly smaller than the posterior one and is subsemi- 

 circular in outline, the convex side ventrad, axis directed nearly straight ectad. 

 The three tentacles arise close together in the anterior furrow of the prostomium, 

 the paired ones lower down than the median. The median is more than twice 

 the length of the prostomium and considerably longer than the paired ones, which 

 are just about twice the length of prostomium. They are strongly jointed, sub- 

 monihform. The palpi are broad, distally rounded, flattened processes united 

 at the extreme base and extending directly ventrad. (Plate 22, fig. 1, 2). 



