MAGELONA PAPILLICORNIS. 225 



marked regions, viz. an anterior with eight pairs of bristle-bundles, a ninth segment sui 

 generis, and a succeeding elongated part composed of a peculiar ninth series of bristles, 

 the rest having a widely separated dorsal division bearing capillary bristles, and a ventral 

 division carrying hooks. Segments 145, and in its native sites the body is extremely 

 elongated and ends in a rounded tip and two short, subulate caudal cirri at the anus. 



The general colour anteriorly (" thoracic " region) is a beautiful pale pink, the long 

 tentacles being of the same hue. The succeeding region of the body is dull greyish or 

 greenish from the intestine. The sides of the body have whitish pigment chiefly developed 

 at the segment-junctions between the bristle-tufts. Ventral surface pinkish, this colour 

 being due to the tint of the blood, which also colours the extruded proboscis of a deep 

 pinkish hue. The tentacles are sometimes banded with black, the pigment occurring on 

 the ventral surface nearly from side to side along the distal two-thirds — that is, in the 

 region of the papillae. 



The first region of the body (Plate CI, fig. 2) has eight bristled segments, and it is 

 characterised not only by its colour and smoothness, but by the somewhat quadrangular 

 outline. On the dorsal surface a distinct median fillet from the muscles (?) occurs, whilst 

 ventrally a broad area with a raised lateral margin passes from the rear of the mouth to 

 the end of the region, and in the last segment it narrows to its termination. The region 

 itself is distinctly constricted posteriorly. 



The first pair of feet are somewhat in front of the median posterior peak of the 

 prostomium. 



The anterior bristles form a double series in each foot. The inferior are simple, 

 delicate, and tapering (Plate CVI, fig. 7), and such have a larger free portion and a more 

 pronounced terminal curve than the more numerous superior series (Plate CVI, fig. 7 a). 

 Both have wings, which, however, are wider in the superior bristles. The dorsal lamella 

 of an anterior foot is shown in Plate CI, fig. 2 a, and the ventral lamella in Fig. 2 b. 



Mesnil's interpretation and figure of the fifth foot differs from the condition in the 

 St. Andrews and other examples observed. He describes a dorsal and a ventral subulate 

 cirrus in addition to the dorsal and ventral lamellas ; broken fragments of lamellas and 

 folds of these peculiar structures simulate cirri, but that is all that can be said. No 

 structure of that kind has been observed. Moreover, he states that the bases of the dorsal 

 and ventral bristles are enveloped by the respective lamellae-like sheaths (d'une sorte de 

 fourreau). This appears to be a misinterpretation of the able French observer. The 

 bristles are never included between the flaps of the lamellae, but are outside these, 

 viz. in front of them, as can be seen in detached feet by focussing, and in situ under a low 

 power. 



Mesnil states that the ventral division of the eighth foot differs from all those in front 

 of it by its great development, but it can only be said that this organ slightly increases 

 from before backward, the seventh being nearly as large. It is probable that he has 

 mistaken the dorsal for the ventral, for the dorsal is the larger, in the form of a scoop- 

 shaped lamella with a larger tuft of the capillary bristles in front ; whereas the ventral 

 scoop-like lamella is smaller, with a somewhat smaller (not shorter) group of bristles. 



The second region of the body is formed by the ninth segment and its feet with their 

 special arrangement. Dorsally is a fan-shaped lamella with a truncated tip bearing a 



152 



