1906.] NATURAL SCIENCES OF PHILADELPHIA. 501 



DESCRIPTIONS OF NEW SPECIES OF POLYCH^TA FROM THE SOUTH- 

 EASTERN COAST OF MASSACHUSETTS. 



BY J. PERCY MOORE. 



Arabella spinifera sp. nov. 



This species is known only from an incomplete worm consisting of 

 the prostomium and fifty-one anterior segments and measuring 18 mm. 

 long and 2 mm. in diameter, indicating a form less elongated than 

 Arabella opalina Verrill, 



Prostomium subcorneal, very slightly depressed, acute, more than 

 twice as long as the basal width; sides straight; ventral longitudinal 

 grooves close together and very faint. The noteworthy elongation 

 of the prostomium may be abnormal, resulting from an injury at the 

 base. Eyes two, rather large, conspicuous, situated on the dorsum 

 close to the posterior border of the prostomium and separated by a 

 space of less than one-third the basal width of the prostomium. 

 Palps rudimentary, or at least not visible from the exterior, and 

 enclosed by the margins of the lips. 



Peristomium and somite II clearly separated by a deep furrow, both 

 dorsally and ventrally ;both simple apodous rings, the former slightly the 

 longer. Posterior lip smooth. Fort-bearing somites all very short, 

 about 5-8 times as wide as long, all clearly defined by distinct furrows, 

 simple in structure, and decidedly more arched dorsally than ventrally, 

 making a subterete bodj'. 



Parapodia begin on III. The first (Plate XIX, fig. 3) consists of a 

 small but prominent notopodium, and a neurapodium which is divided 

 into a short and stout, rounded presetal lobe supported by a single 

 stout aciculum, and a similarly formed but slightly longer postsetal lobe, 

 which is ventral and only slightly posterior to the former. Remaining 

 parapodia (fig. 4) are prominent, and the postsetal or ventral lobe is 

 elongated into a stout cirriform branchial organ containing a large 

 vascular loop. For the length of the piece the parapodia undergo no 

 change, except, first, a slight increase in size of the postsetal lobe and, 

 second, a scarcely perceptible reduction of it in the last ten or twelve 

 somites. 



On the fii'st two or three parapodia the acicula do not project 

 beyond the surface, but the neuropodia of all others are supported by 



