190 PYGOSPIO BLBGANS. 



each side the central process is supported by the buccal expansions and the first segment. 

 The mouth opens on the ventral surface just behind the anterior border, and has a lip at 

 each side. 



The body is about 15 or more mm. in length, of a dull yellowish colour, with a tint 

 of orange, the anterior third being reddish from the blood-vessels. Segments forty to 

 sixty. Twelve bristled segments anteriorly have only the lamellae projecting dorsally, 

 the thirteenth 1 bearing a well-marked branchia to the outer border of which the some- 

 what crenate lamella is fused (P]ate XCIII, fig. 2). Moreover, these segments are 

 narrower than the succeeding. From nineteen to twenty-five pairs of branchiae are 

 ]argely developed, with conspicuous cilia, in a row along the median anterior region 

 (Mesnil says internally), and the branchiae of opposite sides have their ciliated rows 

 connected by an intermediate line of these organs. The longest branchiae are about the 

 posterior third of the series. Mesnil describes the French examples as having generally 

 about eight pairs, though they may reach the number of twenty-three, so that the British 

 representatives appear as a rule to have more than the French, in which Mesnil further 

 states that the branchiae are equally developed throughout. Posteriorly the body terminates 

 in four small whitish conical processes (Plate XCVI, fig. 9 a), which are not ciliated. 



The first foot springs from the side immediately behind the base of the palpus, and 

 bears superiorly an acutely-conical lobe behind the blunt cone of the setigerous process. The 

 bristles are capillary, finely tapered, and arranged in the typical manner, the longer forms 

 being dorsal. The ventral lamella is also conical, and the setigerous process carries 

 similar bristles, which increase in length in the second foot, and at the fourth the ventral 

 lamella is obtuse, whilst the dorsal is less acute. The upper dorsal bristles are long and 

 finely tapered (Plate CVI, figs. 1 and 1 c), whilst the lower and shorter have broader 

 tips with finely attenuate ends (Plate CVI, figs. 1 b and 1 c). All the bristles are dotted, 

 curve backward, and the wider inferior forms occur in the third foot as indicated by Mesnil. 



This type of foot goes as far as the seventh, the eighth having its ventral bristles 

 replaced by winged hooks (Plate CVI, figs. 1 d and 1 e), about four of which occur in each 

 foot. The wings are broad and short, expanded, and smoothly rounded distally, and the 

 shaft has distally a forward curve, then below the wings it bends backward, and only very 

 slightly diminishes from the throat, from which a short sharp main fang passes off at 

 a little more than a right angle, and with a single prominent spike on the crown. 



The tenth foot has dorsally a small conical dorsal lamella with a tuft of long, slender 

 bristles, the upper (and posterior, Mesnil) being the longer and directed obliquely 

 upward and outward. There is little to indicate the ventral lamella except a short and 

 very narrow rim, where the four or, occasionally, five winged hooks emerge. 



The thirteenth foot (Plate XCVII, fig. 8) ushers in a change, for the dorsal lamella 

 now forms an external border to the branchia, a few crenations occurring along its free 

 rim, and a blood-vessel internally forming a loop at the tip and returning. The bluntly- 

 conical setigerous process has four longer and more slender tapering bristles directed 

 upward and outward, followed by the shorter series with very narrow wings. The 

 outline of the foot passes downward with a slight curve outward and then inward toward 

 the row of four winged hooks, the fangs of which point upward. A slight elevation 



1 Mesnil has found them on the eleventh. 



