850 PROCEEDINGS OF THE ACADEMY OF [DeC, 



more than a semicircumference and is very smooth and iridescent. The 

 ventral is much flatter, has deep bounding furrows and a transverse 

 glandular line near the anterior margin. The ventral region slightly 

 exceeds the dorsal in width and embraces it laterally so as to form a 

 shelf or flange supporting the setigerous tubercles. The thoracic region 

 tapers regularly into the abdominal, which differs from it little except 

 in the form of the parapodia and the more prominent lateral muscles 

 and deeper neural groove. The pygidium is much injured on both 

 specimens. 



Branchia have existed in the usual four pairs, but a single one only 

 remains in place. It is nearly terete but somewhat compressed and 

 tapers regularly from the base to the slender subulate tip. Its length 

 is about equal to the width of the thorax or when appressed it reaches 

 somite IX. The scars (fig. 5) show the branchiae to have been more 

 crowded than in A. alaskensis and to arise in a distinctly quadrate 

 group, two pairs on each side. Apparently the two anterior belong to 

 somite IV and the two posterior to V, and the two medial are some- 

 what larger than the two lateral. A shield-shaped area about twice as 

 long as wide is present between the median branchise, reaching from the 

 anterior margin of IV to the middle of V where it meets a transversely 

 extended area limited laterally by the outer pair of branchise. 



The paleoli arise from the dorso-lateral tubercles of III and form an 

 open, spreading tuft, little concave and arising from a small arc. They 

 number but eight or ten and all are slender and curved, with awn-like 

 tips (fig. 7), and the longest reach beyond the tip of the snout. 



The setse tufts on the branchiferous segments are borne on small 

 papillae placed close together just laterad of the branchise. The setse 

 are few in number and much smaller than those on succeeding segments. 

 Remaining setigerous tubercles are cylindrical and quite prominent 

 with small truncate cirri, and bear compact tufts of about twelve setse 

 which are longer, more slender, and more curved than in A. alaskensis. 



Uncinigerous tori are short inconspicuous lines near the posterior 

 margins of the segments just below the setigerous tubercles. Poster- 

 iorly they become more prominent and on the abdominal segments 

 project freely, but are usually so macerated in these specimens that the 

 exact form is doubtful. The one represented in figure 6 shows the 

 thickened dorsal cirrus. 



The uncini (fig. 8) are narrow with very long base lines and five very 

 slender acute teeth very deeply divided at the base. The anterior lig- 

 ament process is rather conspicuous and lies beneath the lowermost 

 tooth, while the posterior ligament process is only moderately devel- 



