238 PIONOSYLLIS ALTEKNOSETOSA 



Pionosyllis alteenosetosa, Be St. Joseph, 1886. Plate LXXXVI, fig. 15 — bristle; 



Plate LXXXVII, fig. 12— foot, 



Specific Characters. — Head generally as in P. prolifera,, but sometimes with an 

 additional pair of eye-specks in front. Median tentacle with twenty, the lateral with fifteen, 

 and the longest tentacular cirrus with twenty articulations. Body somewhat roseate with 

 madder-brown or roseate transverse bands in front; 15 — 28 mm. in length and with 

 110 — 144 segments, the latter having a stolon of thirty-two segments (De St. Joseph). Anal 

 cirri with twenty articulations, and a median pygiclial papilla. Foot with a moniliform dorsal 

 cirrus of twelve segments. Setigerous process carries compound bristles, the bifid tips of 

 which are of moderate length anteriorly and posteriorly, but are shorter in the central 

 region and may have neither spinous edge nor secondary process, which is minute and 

 slants forward, as if a stouter spike at the end of the spinous row. Ventral cirrus some- 

 what fusiform in outline, the tip less tapered than in P. prolifera, with which the ten soft 

 papillae in front of the proboscis and the large single tooth agree. 



Synonyms. 



1886. Syllis (Typiosyllis, Lang.) ulternosetosa, De St. Joseph. Arm. Sc. Nat., 7 e ser., t. i, p. 150. 

 1904. Typosyllt's alternosetosa, Allen. Journ. M. B. A., n.s., vol. vii, p. 219. 

 1908. Syllis alternosetosa, Elwes. Ibid., vol. viii, p. 199. 



Habitat. — Eddystone Grounds, Plymouth (Allen) ; Torquay, between tide-marks 

 (Elwes). 



Dinard, coast of France (De St. Joseph). 



In 1886 De St. Joseph described, under the name of Syllis (Typosyllis, Lang.) 

 alternosetosa, a new species which he had found extremely common both in dredgings and 

 between tide-marks at Dinard. Major Elwes met with the same form in considerable 

 abundance at Torquay, and to his kind courtesy in forwarding mounted specimens the 

 present remarks are due. 



This Syllid bears in size, external appearance, and coloration a near resemblance to 

 Pionosyllis prolifera, Krohn ; and as this widely distributed form shows very considerable 

 variation, both in coloration and the length of the cirri, there is room for re-consideration, 

 especially as Malaquin considers P. alternosetosa identical with S. hyalina, Grube, whilst 

 Giard thinks it is a variety of Syllis cornuta, H. Pathke. The head in these examples 

 closely resembles that of Pionosyllis prolifera, though differing in having an extra pigment- 

 spot in front and shorter tentacles. The median tentacle has about twenty articulations, 

 the lateral fifteen, and the longest tentacular cirrus twenty. The dorsal cirri have about 

 twelve articulations, the anal cirri twenty, and between them is an unpaired median 

 papilla, as in P. prolifera, the papilla in the latter occasionally being bifid, as an 

 abnormality. The cirri and tentacles certainly differ considerably in character, those of 

 P. alternosetosa being shorter and even more distinctly articulated. They are pro- 

 portionally thicker, and taper more abruptly. In the structure of the foot (Plate 

 LXXXVII, fig. 12) the ventral cirri of the two forms diverge, for whilst that of 

 P. prolifera has a tendency to be subulate, that of P. alternosetosa has a tip less tapered, 



