44 THE ANNELIDA POLYCHAETA. 



inflated and vesicular, upper and lower surfaces being decidedly convex, and 

 are essentially smooth. The elytra of the nineteenth somite are smaller, each 

 capping the long elytrophore and extending but little beyond it on each side; 

 it is more nearly orbicular, lacking the indentation on the outer side. 



The neuropodial setae are arranged in a vertical plane in which they spread 

 out in a fan-hke manner. They are of two distinct types in a dorsal and ventral 

 group respectively. The ventral group consists in most cases of two setae but 

 often of three and sometimes of up to four or five in the middle region of the 

 .body, wluch are shorter and stouter than the others with the heads short and 

 not finely extended at the tip. The setae of the dorsal group are much longer 

 and more slender throughout and much more numerous, the number being 

 ordinarily from twelve to eighteen in parapodia of the middle region of the body, 

 becoming fewer in the anterior region. In the ventral type the head is in out- 

 line somewhat like that of the head of a spear with one side slightly concave, 

 the other shghtly convex, with the tip bent a httle toward one side; seriate 

 finely pectinate scales occur along the concave side from base to tip of the head 

 in two partly interlocking series; there is no subapical tooth. (Plate 7, fig. 4). 

 In the setae of the dorsal group the heads are more slender and much more 

 elongate, being drawn out distally above the series of scales into a long, very 

 fine, smooth tip which is commonly more or less curved. In the first metas- 

 tomial parapodia of the type only setae of the first, stout type are present, there 

 being five of these in each; in a paratype a seta of somewhat intermediate form 

 appears. No setae were detected on the peristomial parapodium. 



Locality. Easter Island: 29 miles northeast of North Cape. Sta. 4694, 

 (lat. 26° 34' S., long. 108° 57' 30" W.). Surface. 22 December, 1904. Four 

 specimens. 



It is possible that the type-specimens of tliis species are not wholly grown; 

 but they are so strongly characterized that there is no likelihood of difficulty of 

 recognition. The most salient features of the form are those manifestly adap- 

 tive to its pelagic Ufe, such as the long parapodia and setae, the inflated though 

 small elytra, and particularly the greatly elongate, apparently pneumatic 

 notocirri. As judged by the much inflated and large cirrophores, the style of 

 the notocirri on the sixth somite, missing in the types, must have been of most 

 6 xceptional length. 



