SIGALIOX MATHILDAS. 429 



wrinkles, so that it resembles in a decayed specimen the trachea of an insect. The head 

 is thus raised above these processes, and is confined to the dorsal region. A short 

 conical process on the inner and upper border of the foot may indicate the lateral 

 tentacle. 



Body three to five inches in length, and with segments about as numerous as in 

 Sthenelais boa (180), elongate, very little tapered anteriorly, so that in the preparations 

 it is almost truncate, and gradually diminishing posteriorly, though terminating in by no 

 means a slender tail, from the tip of which a remarkably long and slender caudal style or 

 cirrus extends. The functions of this delicate appendage would appear to be sensory, 

 and it is curious that the tail is often specially modified in sand-dwellers, such as 

 Nephthys, certain Opheliidx, and Spionidae. The dorsal arch is slightly rounded laterally, 

 flattened in the middle when the scales are present, the prominent papillae for the latter 

 occupying most of the surface, and in the ripe forms showing ova through the walls. 

 The ventral surface is in life flattened, and in the preparations usually presents the 

 aspect of a long riband with rounded edges. A segmental eminence occurs at the base 

 of each foot, but no distinct papillae could be made out. 



In life the colour of the dorsum is greyish-brown with a central bluish-green mark, 

 or dull greyish-white or pale pinkish in front with a dark grey stripe from the proboscis. 

 In some a pale brown streak marks the inner margin of each scale. The ventral surface 

 is iridescent, bluish-green or pale pinkish, with the red central vessel. 



Proboscis. — The number of papilla on each side (dorsally and ventrally) is about 

 sixteen, though from overlapping one or two more may occur, e.g. seventeen or eighteen. 

 The teeth bite alternately, the lower passing to the right of the upper. 



Scales (Plate XXXIV, fig. 14) about sixty-four pairs, and of the hue already 

 mentioned. They are firmly adherent. The surface is smooth, and they have the 

 external border supplied with a series of pinnate processes. The first pair are smaller 

 and somewhat triangular in outline, with a series of the typical pinnate processes along 

 the outer border. Moreover at the bases of these are a few simple papillae, and in some, 

 instead of the pinnate process, a group of long, simple papilla? occur at one end of the 

 series. The scales gradually assume a quadrate outline, the outer border bearing the 

 papillae being nearly straight, while the posterior and inner corner is rounded off. The 

 processes 1 (Fig. 83) have a stout central stem, which tapers to a slender point. The 

 axis is granular. The pinnae or papillae arise on the scale even below the process, and 

 are continued on it somewhat irregularly at the base, but by-and-by assume a more 

 uniformly pinnate arrangement. The papillae are pale throughout. Occasionally one of 

 the processes is bifid. In vertical section the dorsal and ventral coverings of the scale 

 are joined by a close series of fibrous strands. Both surfaces are remarkably smooth. 

 As we proceed backwards the scales become more elongated transversely, but again 

 diminish posteriorly. 



The first scale shows no branchial process, but all the rest are provided with such, 

 the organ being long and sickle-shaped as well as richly ciliated. 



Feet. — The second foot is bifid, presenting an elevated dorsal lobe with a tuft of 

 simple, tapering, finely serrated bristles as in the first foot, the spine issuing at their 



1 < Ann. Nat. Hist./ August, 1898, pi. ii, f. 14. 



