336 THE ANNELIDA POLYCHAETA. 



They are highly arched above and flattened beneath, with no distinct neural 

 furrow. They are entire or may show above a vague transverse furrow, and are 

 smooth excepting for a few weak longitudinal sulci. (Plate 62, fig. 3). 



The pygidium is comparatively very small, and bears four, foUaceous, dis- 

 tally narrowed cirri. 



Parapodia, inclusive of processes, mostly about one fourth the width of the 

 body. Uniramous. Neiu-opodium cylindrical, produced at the distal end into two 

 flattened lobes, one postsetal and one presetal. The presetal is short and distally 

 evenly rounded; the postsetal lobe is much longer, and is distally moderately 

 narrowed and is also convexly rounded. The notocirrus, attached to a short 

 cirrophore near the base of the foot above, has the style narrow at base and then 

 expanded into a conspicuous foUaceous blade which is oblong or oblong-lanceo- 

 late in outline, with the distal end usually convexly rounded, or in some (more 

 caudal ones) subacutely narrowed. (Plate 62, fig. 4). 



The setae are arranged in a subvertical hne extending in the crevice between 

 the presetal and postsetal hps and proximad of these on the ventral side. They 

 are of two types. The more delicate, colorless, and transparent capillary setae 

 form the upper part of the series and are much the more numerous. They 

 increase typically in length dorsad. Each is flattened and narrows distad to a 

 very fine tip, and is curved or somewhat angularly bent near, or distad of, the 

 exposed part. The ventral setae, which are of the crochet-type, and ordinarily 

 two in number, are similarly colorless and transparent. They are shorter and 

 much stouter. Toward the distal end each narrows to a cervix at which it 

 bends somewhat dorsad and bears two short, obtuse teeth of which the proximal 

 one is decidedly the larger and is ordinarily weakly bifid, with the upper denticu- 

 lation the smaller. The membranous guards are equal. They scarcely exceed 

 the teeth, and then- distal edge is straight and a httle obhque. (Plate 62, fig. 5). 

 The aciculum is stouter proximally than a crochet; it has a very weak double 

 curve and its acute distal end projects slightly from the surface. 



The mandibles and maxillae are black. The mandibles have stems which 

 are short, acute caudad, and widen clavately cephalad. At the distal end each 

 bears a masticatory plate which is shortly oblanceolate in form; toward the 

 distal end the mesal edge of each presents a weak reentrant angle, and there 

 are a few small weak undulations, or teeth, near this and on the distal edge. 

 There are five pairs of maxillae. Of these the fifth are in the form of simple 

 curved hooks. The fourth are dentate plates presenting at the distal end a 

 longer hook and proximad of this five stout teeth on the right side and four 



