ON A NEW SPECIES OF SCLEROGHKILUS. 409 



base of the fork. The prongs, which are unequal in length, are usually curved, their 

 fine tips pointing away from each other. In the anterior and middle segments the 

 prongs are about 50^ and 35^ in length respectively, and in the posterior segments 

 about 4(V and 25^. Each prong bears along the inner edge of its proximal three- 

 fourths a series of regularly-placed pointed processes. Only the fork and a short 

 portion of the shaft proximal to it project beyond the lips of the chsetal sac. In the 

 middle region of the body there are about eight to twelve furcate chsetse in each of 

 the rami of the parapodia. 



Systematic Position of the Specimen from Scotia Bay. 



The characters of the prostomium, parapodia, and chsetse, and especially the 

 presence of the distinctive furcate chsetse, show clearly that the specimen described 

 above belongs to the family Scalibregmidse. It is referable to the Scalibregma- 

 section * of the family, for the body is sub-fusiform and the prostomium T-shaped, 

 its lateral angles being drawn out to form short tentacular processes. To this section 

 of the family belong the following genera : — Scalibregma Rathke, Pseudoscalibregma 

 Ashworth, Sclerocheilus Grube, Asclerocheilus Ash worth, and Oncoscolex Schmarda. 



The Scotia Bay specimen differs from Scalibregma in several striking respects, 

 e.g. the absence of gills and dorsal cirri, the ventral cirri are much more slender, 

 and there are stronger chsetse in the first and second notopodia, whereas such chsetse 

 are not present in Scalibregma. Further, Scalibregma rarely possesses eyes.t 



The genus Pseudoscalibregma was suggested by the writer \ to contain certain 

 little-known, abranchiate worms resembling Scalibregma in general appearance, but 

 their real relationship to Scalibregma remains to be ascertained. These worms 

 appear to agree in their external features with Scalibregma, except in regard to the 

 absence of gills, and so differ from the Scotia Bay specimen in the parapodial and 

 chsetal characters mentioned above. 



The. characters of Asclerocheilus are little known, but the single species — 

 Asclerocheilus intermedius (=Li2^obranchius § intermedius Saint-Joseph) — referred 



* See the classification suggested by the writer in Quart. Journ. Micr. Sci., vol. xlv (1901), pp. 296, 297. 



t I have examined about sixty specimens of Scalibregma varying in length from 4 mm. to 56 mm., and including 

 five epitokous examples. Eyes are present in only two specimens, both ordinary non-epitokous forms. For one of 

 these specimens, which has been in my possession twelve years, I am indebted to Dr E. J. Allen, F.R.S., who 

 collected it near Plymouth ; for the other, collected in 1911 at Cap Levi, near Cherbourg, I have to thank Professor 

 Fauvel, who, on finding that this specimen possessed eyes, kindly sent it to me for examination. Both specimens 

 are similar in size, but only one — the Plymouth specimen — is complete ; it is 30 mm. in length. In both, the eyes 

 are on the right and left sides of the prostomium, and are wide apart, i.e. do not approach each other like those of 

 Sclerocheilus. I have stained and cleared the Plymouth specimen, which exhibits on each side two eyes adjacent to 

 each other, composed of a series of closely associated simple eyes, which in section are found to be similar in structure 

 to those of Sclerocheilus. 



I See Quart. Journ. Micr. Sci, vol. xlv (1901), pp. 291, 292. 



§ The genus Lipobranchius founded by Messrs Cunningham and Ramage to contain the species L. jeffreysii 

 ( = Eumenia jeffreysii M'lntosh) cannot well contain also L. intermedius Saint-Joseph, which differs from the former 

 in several respects, but especially in the nature of the chsetse of the first and second notopodia. A thorough revision 



