260 HETEROCIttRITS ATER. 



is dark. The mouth opens -ventrally a short distance behind the tip of the snout as in 

 other forms, and not at the tip as De Quatrefages observes. 



^ Body 1 to 2 inches in length, rounded or slightly flattened in front, more 

 distinctly flattened after the anterior third, and often showing a broad oar-shaped outline 

 posteriorly before abruptly narrowing to the tip, which presents a papilla on each side at 

 the vent. The body is slightly tapered toward the snout, and the segments throughout 

 are distinctly marked, their anteroposterior diameter being larger in front than behind. 

 The first four or five bristled segments are narrow. The dorsal and ventral divisions of 

 the feet are evident. 



The colour is very dark blackish-green throughout, the tentacles being pale green 

 with a central red streak. It tinges spirit green, giving out a dark green exudation just 

 as dark green specimens of Girratulus do. 



In the intestine of an epitokous form fragments of fine alga3 were present. 

 De Quatrefages thought that the buccal segment was in abeyance (" L'anneau buccal 

 a presque entirement disparu"), but not only the mouth-parts but also the origin of the great 

 tentacles probably pertain to the peristomium. The large tentacles are prominent organs 

 with a deep groove on their ventral surfaces, the edges of which in the preparations are 

 crenated, and thus in all probability they approach in function bo those of Polydora and 

 other Spionidse. Above and behind the tentacles is a branchia, and as a rule three others 

 follow, each on the dorsal arch of its segment, and with a diminishing transverse distance 

 between the bases. They are of moderate length, and in some have a tendency to form 

 curves and a few coils. 



Behind the tentacles are indications of five segments, but whether the imperfect 

 first of these should be regarded as an independent one may be an open question. The 

 four following have dorsal and ventral bristles of a simple tapering kind minutely 

 serrated along the anterior edge (Plate CVII, fig. 8). These and the next are all narrow 

 segments and differ in this respect from those which follow. The first is represented by 

 a dorsal and a ventral setigerous papilla with a ridge between. 



This type of foot changes at the seventh, where the characteristic hooks or crotchets 

 occur in the ventral as well as in the dorsal division. On their first appearance these 

 organs have a slight forward bend of the shaft as far as the distal third, where a faint 

 backward curve takes place. The shaft shows only a slight dilatation from the base a 

 short distance upward, remaining nearly of the same diameter to the neck, where it bends 

 backward and again forward at the tip. The tip in certain anteroposterior views 

 shows a median rib and two lateral wing-like areas, but probably this appearance is due 

 to the thicker tissue in the centre and the thinner and slightly expanded lateral regions. 

 In lateral view (Plate CVII, fig. 8 a) the hollow of the distal hook appears to be scooped 

 out like the old snuff-spoon, while an antero-posterior view shows a bluntly-conical point 

 (ibid., fig. 8 b). These hooks increase gradually in strength though not in length 

 posteriorly in both divisions of the foot, and their number toward the tip of the tail 

 diminishes, but they are of great proportional size. Two occur in the dorsal and three 

 in the ventral division just in front of the tail, but the number seems to vary. The 

 alterations of the contour of the tips of these hooks would indicate that they have special 

 functions in connection with the tunnel, and their gradual increase in strength from 



