412 STHENELAIS BOA. 



secondary process, so that the end is like a bird's beak. Those at the ventral edge 

 again are much more slender, have a slightly dilated spinous region, and a five-jointed 

 bifid appendage. Two groups of clavate papillae occur on the edge of the foot above 

 them and a row of smaller papillae at their bases ventrally. The ventral cirrus extends 

 fully as far as the fleshy part of the foot, and internal to it is a funnel-like, ciliated 

 process. 



The typical foot (Plate XXXI, fig. 5) presents dorsally a richly ciliated branchial 

 process somewhat subulate in outline, and which is evident at the fourth foot. Beneath, 

 on the dorsal curve, are three T-shaped ctenidia. Another ctenidium lies on the posterior 

 border of the foot deeply placed in the interpedal fissure. In the middle of the body others 

 occur on the dorsum of the foot and behind the elytrophore. Pruvot and Racovitza observe 

 that they all have the same structure, viz. conical epidermic cells with their bases at the 

 broad end and their points at the pedicle of the organ; they are richly ciliated distally. 

 The dorsal lobe is considerably less than the ventral; the bristles (Plate XLI, fig. 19) are 

 long, slender, and boldly spinous from a little above the base to the tip. Viewed from the 

 side they form a beautiful fan directed laterally with the digit-like papillae at the anterior 

 border of the base. Though slender they are somewhat stiff and curved — with the 

 concavity upward (Plate XLI, fig. 20). The spines form even transverse rows, 

 thus differing from the alternate series so common in this group and in the 

 Polynoidae. The transverse arrangement, however, may render them more brittle. The 

 dorsal lobe is separated from the ventral by a deep fissure, and has a series of long 

 papillae at its tip. The ventral lobe is massive, with a truncated extremity which bears 

 the spine in its middle, and usually a single digit-like papilla. A fold of skin, 

 arising at the upper part of the lobe, passes down posteriorly and curves to the front, 

 separating the more slender ventral bristles from the stout series. In the posterior part 

 of the body the commencement of this ridge of skin forms a free flap. The upper group 

 of the ventral series consists of the moderately stout forms with the simple spinous tips 

 (Plate XLI, fig. 21), and also a few with about three joints to the tapering, bifid 

 appendage, the tip of the shaft having a few rows of spines. The centre of the foot is 

 occupied by a series of stout shafts bevelled at the tip, and with a short appendage of one 

 segment (Plate XLI, fig. 22), and the beak-like, bifid extremity. In some, transverse 

 striae indicate traces of spinous rows. Those of the upper series have longer and more 

 slender appendages. Ventrally is a group of slender bristles forming a row directed 

 forwards and outwards, then downwards and outwards, each with a few rows of spines 

 on the expanded distal end of the shaft and appendages of one to four joints (Plate XLI, 

 fig. 23). These spring from a notch at the ventral edge and within the tip of the foot, 

 the inner border of the notch being marked by a series of small papillae. In the region of 

 the spine, which pierces the middle of the foot, is a long and somewhat fusiform papilla. 

 So far as the structure of the bristles is concerned, the type remains the same in the 

 terminal feet, though the bristles diminish in size. The median stout bristles have longer 

 and more slender hooked appendages, and the backward curve of the end of the shaft 

 is more marked. The papillae are fewer. The ventral cirrus is subulate and tapering, 

 extending to about the tip of the fleshy part of the foot. A spur or process occurs at 

 its inner border above the basal segment. A well-marked ctenidium is placed a little 



