DASYBRANCHUS CADUCUS. 287 



examples in numbers in the fissures of rocks at St. Jean-de-Luz and other places on the 

 shores of France (De St. Joseph) ; Naples in deep water (Lo Bianco) ; Cape of Good Hope 

 (Mcintosh). ■ 



A large form, some of the fragments being about 4 in. in length and 6 to 8 mm. in 

 diameter. It is distinctly tapered anteriorly, gradually enlarges toward the middle and 

 again probably tapers posteriorly, but as the specimen is incomplete this is conjectural. 



The head (Plate CI, fig. 4) forms a short blunt cone which in the preparation is 

 partly withdrawn into the peristomial segment, which is marked dorsally by a somewhat 

 regular series of longitudinal striae over an eminence. Ventrally the proboscis is pro- 

 truded as a short cylinder with a corrugated and slightly glistening surface from tuber- 

 cular or papillose longitudinal ridges. In the preparation the peristomial segment 

 forms a blunt cone, and besides the eminence a differentiation of the longitudinal striae a 

 little in front of the middle dorsally and the presence of a transverse depression may indi- 

 cate a sensory organ. Whilst this segment is undivided ventrally, a deep transverse 

 furrow dorsally cuts off a posterior belt. Such may be an indication of the arrangement 

 of the succeeding rings. The segment following the foregoing has the type of the thirteen 

 which constitute the region, viz. is two-ringed, the middle sulcus having a broad papilla 

 on each side dorsally directed backward, and bearing a tuft of bristles (PI. CVII, fig. 15) 

 which have a long, slightly curved shaft ending in a finely-tapered tip with wings. The 

 symmetrical arrangement of the setigerous process is a feature it has in common with 

 Notomastus. 



The anterior region has a characteristic differentiation of the two rings of which the 

 segments are composed, viz. in mid-dorsum is a straight line, bevelled, however, when it 

 approaches the bristle-tufts, then laterally are two fillets, the upper being the smaller, 

 whilst the long ventral line is bevelled at each side near the bristles. On the other hand 

 the ring in front of that in the line of the bristles shows no special differentiation other 

 than the setigerous processes posteriorly. The rings become proportionally narrower 

 toward the termination of the region, at the fourteenth bristle tuft. The same arrangement 

 of the fillets, however, occurs in the second ring for two or three segments, and then the 

 fillets diminish to a single lateral papilla marking the separation of the dorsal rows of hooks 

 from the ventral, the dorsal showing a lateral tumefaction on each side and a median de- 

 pression in the preserved example, and the ventral a long lateral ridge separated from its 

 neighbour only by the linear furrow over the nerve-cord. By-and-by a dark speck below 

 the papilla probably indicates the aperture of the branchial organ. 



In the posterior region the chief changes are the increase of the median dorsal space 

 and the occurrence of a shorter interval between the now short tori and the lateral 

 papilla. The tori indeed project dorso-laterally as isolated cushions. Ventrally, again, 

 the median furrow separates two short tori, with the branchiae at their outer borders, and 

 the lateral papillae have become more or less ventral. The space between the dorsal and 

 ventral tori is longitudinally striated. The same arrangement continues to the tip of the 

 tail, though the prominent features are toned down as the tail gently tapers, and the anus 

 is dorsal. 



The hooks occupy a ventro-lateral position not far removed from the dorsal arch, and 

 thus in a ventral view they escape notice. They occupy a similar position with regard to 



