MALDANE SARSL 345 



collar posteriorly a prominent median ridge, with a converging oblique muscle on each 

 side, curves upward and passes forward to the thin conical anterior plate, upon which it 

 is lost. In some the ridge is distinctly notched in lateral view. On each side of its base 

 anteriorly are the nuchal grooves, a line from which passes to the notch on the margin. 

 In the majority of specimens slight grooves, which run obliquely forward and outward 

 from the median ridge, give a resemblance to a leaf with its midrib and veins. The 

 mouth opens a short distance behind the anterior border of the cephalic plate, and appears 

 as a puckered dimple, often with a groove in front in ordinary preparations, which often 

 have the snout bent at an angle to the trunk, the mouth being thus carried outward. The 

 peristomial segment is covered dorsally by the cephalic plate and is thus thrust ventrally. 

 It bears no bristles or hooks. 



The body is continued behind the cephalic plate as a more or less cylindrical region, 

 though much depends on its preparation. Thus some removed from their tubes are quite 

 cylindrical, whilst others, killed in the free condition, show numerous segmental con- 

 tractions and dilatations. Slight diminution occurs just in front of the caudal disc when 

 viewed from above downward, but, on the other hand, a distinct dorsal increase, terminat- 

 ing at the vent, is evident in lateral view. The dorsum is generally convex throughout, 

 but the ventral surface is more or less flattened, especially after the anterior fifth, where 

 it is ringed and marked by a median line (nerve-cord), which toward the terminal fourth 

 is sunk in a groove, rising, however, toward the caudal plate. The anus terminates 

 dorsally at the end of a ridge, and the margin is slightly crenate. Moreover, a separate 

 papilla just in front of the caudal plate aids in its closure. Occasionally a prolapse of the 

 gut occurs as a flask-shaped hernia, with the narrow neck at the vent. In this the 

 circular and longitudinal fibres of the gut, as well as a thin chitinous layer, are conspicuous. 

 The caudal plate is slightly oblique with regard to the axis of the body, sloping from 

 above slightly downward and forward. In large specimens the most conspicuous rim is 

 the ventral, which forms a collar as far upward as the median notch on each side, above 

 which is a smooth edge, and then the ventral border is marked by about six crenations. 

 Bach of these is comparatively broad, with a dimple or depression in the middle of the 

 free edge. They are best seen in large examples. The rim continues upward as a slightly 

 oblique collar, which has a tendency to be flattened out at the dorsal edge, where it is 

 also somewhat narrowed, though in a large example this is not evident. The general 

 shape is ovoid, with a tendency to a somewhat narrower dorsal end. A slight median 

 ridge occurs from the dorsal to the ventral edge, stopping short of the collar in each case. 



The peristomial segment has no feature of note except the presence of a lateral 

 furrow on each side from the notch on the cephalic plate. This groove passes backward 

 to the sixth bristle-series running before the glandular elevations and hook-rows ; and in 

 some it may be traced a little further backward. The first bristle-bearing segment, like 

 the adjoining, is shorter than those in the centre of the body and more deeply 

 pigmented. Moreover, as Arwidsson has shown, it is largely supplied with glands, 

 and also has non-glandular streaks. The bristles occur as a tuft on each side, and have 

 fairly stout shafts with a short wing dis tally on the tapering tip (Plate CX, fig. 8 b), 

 which is comparatively short and peculiarly curved. This and the next five segments 

 are shorter than those in the middle of the body. 



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