352 



PROCEEDINGS OF THE ACADEMY OF 



[July, 



DESCRIPTIONS OF TWO NEW POLYCHJSTA FROM ALASKA. 

 BY J. PERCY MOORE. 



Among a number of Alaskan Polychseta in the collections of this 

 Academy, the two of which the descriptions follow are new. 



Syllis quaternaria sp. nov. 



This sexual free-swimming form of the type for which Malmgren 

 instituted his genus Chcetosyllis is probably the epitokous form of a 

 true Syllis, but it cannot be correlated with any atokous form hitherto 

 described. 



The length varies from 7 to 9 mm.; the width between the ends of 

 the parapodia is .8 mm. and between the tips of the capillary setsB 4.5 

 mm., or one-half the length of the body. 



Syllis quaternaria. — a, dorsal view of prostomium, peristomium and first two 

 somites bearing capillary setse, X 24; 6, parapodium from IX with setse cut 

 off, X 32 ; c, a long and d, a short notopodial seta from X, X 600. 



The prostomium (a) consists of a pair of prominent hemispherical 

 lobes separated by a deep, narrow, median cleft, and each again divided 

 by a shallow transverse groove. A pair of simple unjointed or obscurely 

 wrinkled cylindrical tentacles arise from the latter grooves and 

 incline decidedly toward the dorsum. They reach a length of 1|- to 1-J 

 times the prostomium. No other cephalic appendages exist, but there 

 are two pairs of dense, black or deep brown, short spindle-shaped eyes, 

 each provided with a small cuticular lens. The dorsal eyes are the 

 more posterior and look vertically upwards ; the large ventral pair look 

 downwards, forwards and outwards. Sometimes 1 or 2 small, rod-like 



