HYALINOECIA TECTON. 313 



reduced and project on the outer side of the bases of the branchiae only as very 

 short subulate processes. 



The branchiae begin on somite XVIII, XIX, or XX either symmetrically or 

 farther forward on one side than on the other. Thus, on one specimen they 

 appear first on somite XVIII on the right side, and on somite XX on the left. 

 They seem most commonly to appear first on somite XX. They increase in 

 length gradually, and commonly reach a maximum length between somites XL 

 and LX, where their length may equal or slightly exceed the width of the somite. 

 The branchiae are flattened, but narrow and acutely pointed. Each at present 

 shows a shallow longitudinal furrow over the large axial blood-vessel. They 

 occur caudally on all excepting the last two or three somites. 



The neuropodial acicula are yellow in color. They are mostly four in 

 number in each parapodium. They are stout, nearly straight, and acutely 

 pointed, the tips projecting freely from the surface. The setae of the first 

 parapodia are simple, stout, distally acuminate and entire, and are evenly and 

 moderately curved, aciculiform. The tips of some are finely acute, those of a 

 second, stouter type, more rounded. They may show a very fine roughening 

 distally in the form of sublongitudinal lines, and some more proximally show 

 annular impressed lines. (Plate 39, fig. 1,2). These on succeeding parapodia are 

 replaced by simple, much finer setae, each of which ends in a lanceolate limbate 

 blade drawn out to an exceedingly fine tip. The setae are curved at the junction 

 of the slender shaft and the broader blade, while the blade itself is more or less 

 evenly curved in the opposite direction, the fine colorless tip again bending back 

 in the other direction. The limbi are very narrow and are crossed by obUque 

 striae, as usual. (Plate 38, fig. 9). The setae of the ventral group have the 

 blades shorter than those of the dorsal group. (Plate 38, fig. 8). In the middle 

 and posterior regions there appear in each fascicle two, and sometimes three, 

 darker hooked setae or crochets. These are shorter than the limbate setae. 

 Each is moderately curved and narrowed below the teeth. The teeth, which 

 are protected by the usual membranous hood, are stout and subequal, each con- 

 vex on its ectal edge and straight on its inner, or the upper one a httle concave; 

 the two are at a moderate angle to the axis. (Plate 38, fig. 6). Associated with 

 the setae of the dorsal fascicle is a tuft of much shorter, very fine and delicate 

 setae, each of which ends in a clavately expanded plate bent into a half or three 

 fourths hollow cone, like a funnel with a sector removed. The fine distal edge 

 is pectinate, as usual, and the surface often appears roughened with longitudinal 

 lines and with punctae. (Plate 38, fig. 7). 



