36 SCALIBREGMA INFLATUM. 



Body (Plate LXXXVIII, fig. 4) about 3 inches in length, abruptly tapered in front, 

 more gently diminished posteriorly, and closely ringed besides being tesselated throughout, 

 the surface, indeed, resembling a pavement of minute square red bricks. These markings 

 disappear in imperfectly preserved examples, and thus are absent from representations 

 made from them; yet Rathke faithfully shows and describes them. The peristomial 

 segment is two-ringed and achaatous. The mouth opens on the ventral surface between 

 this and the first bristled segment, and is bordered by papillae or ridges in front and 

 behind. This position is such that at first sight it seems to open on the segment behind 

 the peristomium. The next three have three rings, the middle bearing the foot. All the 

 succeeding segments have four rings, the feet being on the third ring in each. The last 

 four segments are devoid of feet. The body is terminated by a papillose vent, beneath 

 which are four or five cirri, the latter number having also been found by Dr. Ashworth. 1 

 In small examples dredged by Canon Norman in Norway the caudal cirri are unusually 

 long and slender. 



In life the animal is of a dull brick-red throughout, the tesselated portions being 

 minutely dotted with yellow. The posterior region of the body is often discoloured from 

 the contents of the gut, being dull greyish, and thus throwing the paler lobes of the feet 

 into relief. A slight iridescence occurs on the ventral surface, along which the large 

 ventral blood-vessel passes. 



The branchiae commence on the first bristled foot, and increase in size from the first 

 to the fifth and last tuft. In smaller specimens from the West Coast of Ireland only four 

 branchiae are present, but as the first even in a large example in life is very small, such 

 may be due to retraction within the surface. 



Certain specimens agree in all respects with the typical form, but the branchiae are 

 entirely absent, and Dr. Ashworth states that he has observed the same condition in a few 

 American examples. It is a question whether such should be regarded as specifically 

 different. 



The anterior feet are represented by a pad bearing the dorsal and ventral papillae, 

 but about the eighteenth they become more prominent, and a small dorsal cirrus appears 

 above the setigerous lobe, and by-and-by a ventral cirrus is evident, and both assume 

 considerable prominence posteriorly. A retractile sensory papilla with a tuft of sensory 

 hairs occurs between the dorsal and ventral lobes of the foot. 



The anterior bristles (Plate CIII, figs. 7 and 7 a) are of considerable length, translucent, 

 finely tapered from base to apex, and smooth. None of the forked forms occurred in 

 front, but they appeared before the twentieth foot, and whilst the long simple forms 

 extend far beyond the setigerous papilla, these (Plate CIII, fig. 7 b) project but little beyond 

 the surface, though they probably can be exerted to a greater extent, as indeed they 

 frequently are in the posterior feet (e.g. beyond the thirtieth). The muscles moving the 

 bristles are developed as long narrow slips, and, as the axes of the two kinds of bristles 

 usually differ, their functions probably diverge. 



In the middle line between the dorsal and ventral divisions of the foot is a rounded 

 papilla, the lateral sense-organ of Ashworth, who gives a careful description of its structure. 



The first bristles occur on the second body-segment, and in this and the following 

 Quart. Journ. Micr. Sci./ vol. xlv, N.S., p. 244. 



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