206 THE ANNELIDA POLYCHAETA. 



somites of which sixteen are setigerous, the heteronereid of about sixty, giving 

 a total of nearly seventy-seven. The anterior division is of uniform width from 

 its caudal end to the middle, from where it narrows a little forward to the pros- 

 tomium. The posterior division is widest near its anterior end from where it 

 narrows uniformly to the caudal end. 



The prostomium is quadrangular with a much narrower median process 

 extending forward in front of the eyes. It is wider than the total length in 

 about the ratio eight to seven. The preocular process has above a shallow, 

 median longitudinal furrow. The four eyes are equal and moderate in size. 

 Those of the two pairs are the same distance apart and the two of each side are 

 contiguous. The lens of each anterior eye is directed dorsocephaloectad, that 

 of each posterior one dorsocaudoectad. The tentacles are attached on the lower 

 border of the preocular lobe and project cephaloventrad. They are slenderly 

 subulate. The palpus is attached caudoectad of the corresponding tentacle, 

 below the angle at the junction of ocular and preocular divisions of prostomium, 

 and projects a little cephaloectad of ventrad. The proximal article is long and 

 thick, a little compressed, so as to present an elliptic cross-section; the apical 

 article is small and distally rounded. (Plate 33, fig. 1). 



The peristomium is, as a whole, shorter than the succeeding somite. It 

 is divided by a distinct transverse furrow as in caenocirrus ; the anterior division 

 is the shorter, is again divided by a secondary furrow and is mesally usually 

 convex, but does not project over the prostomium as it does in caenocirrus. 

 The tentacular cirri are all comparatively short, slender, gradually tapered, 

 and closely jointed or varicose. Of the four pairs the posterior dorsals are long- 

 est, but reach only to the fifth or beginning of the sixth somite. The posterior 

 ventrals and anterior dorsals are equal in length, reaching to the third somite. 

 The anterior ventrals are shortest, reaching only to the second somite. The 

 tentacular cirri are attached in the usual places. (Plate 33, fig. 1). 



The metastomial somites of the nereid division of the body are dorsally 

 high and convex; ventrally the arch is lower and mesally flattened and with 

 a rather deep neural fm'row. They are smooth and entire. These somites 

 increase in length to near the fifth, after which the length remains uniform or 

 nearly so. In those of the middle and posterior parts of the division the width 

 is three and three fourths to four times the length. In the heteronereid division 

 the somites are more compressed dorsoventrally and are shorter and more 

 closely arranged. The pygidium is very small, somewhat trapeziform in outline, 

 with the caudal margin notched. No cirri are present in the type. 



I 



