1909.] NATURAL SCIENCES OF PHILADELPHIA. 277 



At first they are long, narrow ridges reaching nearly to the middle 

 line and bearing a single series of about sixty uncini. Posterior to the 

 setigerous region the tori are shorter and thicker and bear only about 

 forty uncini. 



Uncini are small and delicate, the base with prominent posterior 

 angle, the rostrum slender and acute and about half as long as the 

 base, crest with two large profile teeth. Anterior uncini (PL IX, 

 fig. 52) have the base less produced and blunter in front than those 

 from posterior tori (PI. IX, fig. 53). 



The uncini closely resemble those of P. nervosus v. Marenzeller, 

 but the latter has thirty-two setigerous segments and differs in the 

 character of the tentacles, the ventral plates and other features. 



Besides the type there is one additional incomplete specimen, both 

 having been taken at San Diego. 



AMPHICTENIDiE. 



Pectinaria brevicoma Johnson. 



Pectinaria brevicoma Johnson, Proc. Bos. Soc. Nat. Hist., XXIX (1901), pp. 

 423, 424; PI. 15, figs. 151-156. 



A single specimen taken at Delmonte wharf, in the vicinity of 

 Monterey Bay, on July 12, 1904, agrees with Johnson's description. 

 The tube is constructed of coarse sand grains. 



OAPITELLID^J. 

 Notomastus tenuis sp. nov. (Plate IX, fig. 55). 



A slender elongated worm, the single example of which is macerated 

 in the middle but well preserved at the ends. The two pieces prob- 

 ably represent a nearly or quite complete worm which is 118 mm. 

 long and .8 mm. in diameter. Thoracic segments number 12 and 

 abdominal 191. The thorax of 12 segments is clavate, the anterior 

 half thickened, the posterior gradually narrowed, the abdomen 

 abruptly expanded to equal the maximum width of the thorax, then 

 tapering gently to the pygidium. 



Prostomium conical, pointed, with a few specks of pigment scattered 

 along the sides; when retracted somewhat inflated and completely 

 closing the mouth. 



Peristomium simple, achsetous. Thorax clavate, terete, smooth 

 and scarcely iridescent, the intersegmental furrows faint; widest seg- 

 ment about two-fifths as long as wide, narrowest two-thirds as wide 

 as long, most of them equally and obscurely biannulate, the inter- 

 annular furrow with a backward bend or inset into the succeeding one 

 at the position, 7 of , the lateral organs. Neuropodia and notopodia 



