On a New Species of Sclerocheilus, with a Revision of the Genus. By J. H. 

 Ashworth, P.Sc., Lecturer in Invertebrate /oology in the University of 

 Edinburgh.* (With One Plate.) 



(MS. received M;iy 4, 1!)]-). I lead May 2f>, 1914. Issued separately July 2, 1915.) 



CONTENTS. 



Observations on a Specimen of " EUHU uia ncnlata" 303 



i-H'-lirilim Grube, emend. .... 306 



Sclerocheilus minutiis Grube . . . :jn7 



Selerorheilus antarctic us n. sp 309 



! iption of Plate 310 



Description of the Specimen collected in Scoi.ia Ray, 



South Orkneys ....... 293 



Systematic Position ot'thu Specimen from Scotia Bay 297 



Observations on Scli'roclieilus minittus ( Jrube . . 298 



Observations on Sclerocheiltts pacificus J. P. Moore . 302 



Sclerocheilus euros Saint-Joseph .... 303 



The Polydin'te family Scalibregmidae comprises seven genera, the limits and inter- 

 relationships of which are, however, still imperfectly known. The present paper 

 results from a detailed study of one of these genera, a new species of which is de- 

 scribed, chiefly from a specimen collected in Scotia Bay, South Orkneys, and entrusted 

 to me for examination by Dr W. S. BRUCE. 



DESCRIPTION OF THE SPECIMEN COLLECTED IN SCOTIA BAY, SOUTH ORKNEYS. 



This specimen, the only Scalibregmid found by the Scottish National Antarctic 

 Expedition, was dredged on a stony bottom in ten fathoms at Station . -> >25, in Scotia 

 Bay, South Orkneys (hit, (it) 4:j' 42" S. ; long. 44 :}' 33" \V.), in August 1903. 



The worm, which is yellowish brown in colour (in alcohol), is ] '.) mm. long. The 

 anterior portion is broad ; the maximum breadth, 3 mm., is reached about the level 

 of the 10th segment; from this region the worm tapers gradually to the anal seg- 

 ment. The dorsal surface of the worm is strongly convex ; the ventral surface is 

 flattened, and there is a well-marked depression which extends alon^ the mid-ventral 

 line from the 2nd eha't ii'erous segment almost to the anus. 



The prostomium is drawn out at cadi side into a stout, bluntly conical process 

 (Plate, fig. 1 ). On the middle region of the dorsal surface of the prostomium 

 there is a A-shaped area of dark-brown pigment representing the eyes. The point of 

 the A is median, and is situated near the centre of the prostoniiuin ; each limb of this 

 pigmented area passes obliquely backwards and down the. side of the prostoniiuin. 



The perist om i urn consists of a single, aeha-tmis ring, which is incomplete yen 

 trallv, where it forms the antero-lateral borders of t lie mouth (tigs. 1, _>). 



* A grant in .ii'l Hi ill.' i-xp.-inr* inniriv.d dimn;,' lliis iv-caivli hi- lin-n rt-i-i-ivi-d from tin- Karl of Moray Endow- 

 ment of the University of Kflinlmrnli. Tin- cost, of the woodcuts and of ihe rrprodnrt.ion of the liguras on the jilate 

 h.i- liri'ii defrayed l>v tin 1 Carnegie Trust for tlie Uiiiveraitii'" of So.tUnd. 



, (KEI'KINTKI) KKOM TIIF. Tit ANSACTIONS OF THK RdY.M. SOCIKTV OF Kill X IITHi ;H, VOL. L, PP. 405-4'2i.) 



