SYLLIS GRACILIS. 203 



The somewhat long terminal process of the bristles and the presence of a minutely 

 bifid tip in this form, which may be a young example, would show its relationship with 

 Syllis comiita, H. R., but the upper bristles did not attain the length of the ordinary 

 examples of that species, a feature, however, which may be due to age. Moreover, the 

 prominent spines of the typical species were not seen. It has been thought desirable, 

 however, for the present to regard it as a variety of Syllis cornuta. 



9. Syllis gracilis, Grube, 1840. Plate LI, fig. 3; Plate LXX, figs. 25 and 25 a — foot; 



Plate LXXIX, figs. 17-17 c— bristles. 



Specific Characters. — Head broader than long, with four small black eyes, the anterior 

 pair the larger and wider apart. Palpi slightly tapered and transversely striated. Median 

 tentacle has about eighteen segments, the lateral twelve, and the tentacular cirri eighteen. 

 Body of numerous segments (eighty or more) and of a brownish hue, paler anteriorly, the 

 intestine giving a dark brownish colour to the central region from the proventriculus 

 backward. The buds are purplish. The anterior cirri have from twenty to twenty-five 

 segments, but they soon diminish to fifteen or sixteen. 



Two anal cirri of moderate length (thirteen segments) with a distinct median papilla 

 ventrally. The anterior border of the proventriculus is at the twelfth segment, and it 

 reaches to the seventeenth. The foot in the anterior third has a dorsal cirrus of sixteen 

 segments, tapering towards the tip. Setigerous region forms a short cone. The enlarged 

 distal ends of the shafts of the bristles are smooth. The distal piece is long, spinous on 

 the edge, terminating in a well-marked hook with a minute tooth beneath. The distal 

 pieces diminish in length from above downward. The ventral cirrus is long and lanceolate, 

 projecting considerably beyond the tip of the setigerous region. The middle region of 

 the body has two greatly-developed bifid bristles, the strongest of which has no inter- 

 mediate teeth in the fork, whilst the other may have an intermediate spike or two. In the 

 posterior third a tendency to the growth of a separate spur at the tip appears in one of 

 these. In the posterior fourth a single strong bristle occurs, the end of the shaft being 

 bevelled, and a stout terminal piece appended, its tip usually being indistinct. It is 

 flanked on each side by a bristle of the type seen in front, viz., with a long terminal piece 

 and a bifid tip. The stout bristles gradually disappear so that in the last twelve segments 

 or thereabout only the falciform bristles remain. 



Synonyms. 



Grube. Akt. Echin., etc., p. 77. 



Delle Chiaje. Descriz., iii, p. 95; v, p. 101. 



Grube. Fam. Annel., pp. 61 and 132. 



Claparede. G-lanures, p. 77, pi. v, f. 3. 



De Quatrefages. Annel., II, pp. 24 and 644. 



Claparede. Annel. Nap., p. 193, pi. xv, f. 3. 



Marion and Bobretzky. Ann. Sc. Nat., 6 e ser., t. ii, p. &3. 



Webster. Trans. Albany Inst., ix, p. 17, f. 6. 



1840. i 



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