414 DR J. H. ASHWORTH 



Ireland, possessed, in the usual position, two cirri practically equal in length and 

 arising close together. 



A small lateral sense-organ is present just ventral to the base of each 

 notopodium, i.e. in a position corresponding to the " Seitenorgan " of Scalibregma, 

 and its retractor muscle is usually related to the notopodial musculature. Each 

 sense-organ is (in the larger segments) a convex elevation of the epidermis, about 

 50ju long and 20/x wide, traversed dorso-ventrally along its middle by the " hair-field " 

 bearing long, delicate sense-hairs. # Between the sense-organ and the neuropodium 

 there is invariably an epidermal papilla of considerable size, the cells of which are 

 glandular, some of them (" bacilliparous follicles," Claparede) producing curious rod- 

 like secretions, usually sinuous in form. 



The number of chsetiferous segments in the complete specimens examined 

 varies from 44 to 52. 



The anal segment or pygidium bears long cirri, slightly thickened at their 

 distal ends (fig. 9). These cirri are solid, like the neurocirri, being composed of 

 epidermal cells with an axial strand of connective tissue and nerve-fibrils. There 

 is evidently some variation in the number of the anal cirri. Of the six specimens 

 with complete anal cirri which I have examined, one has five and each of the others 

 four cirri. Grube described and figured four cirri in his original account of the 

 species ; Saint-Joseph states that there are five or six ; and Professor M'Intosh 

 and M. and Mme. Dehorne found five in their specimens. 



The Scotia Bay specimen agrees with Sclerocheilus minutus in the form of the 

 prostomium and the presence thereon of pigmented eyes, in the division of the 

 segments into four annuli, in the general characters of the parapodia and in the 

 presence thereon of lateral sense-organs, in the possession by the posterior segments 

 of neuropodial cirri, in the presence of anal cirri, and in the absence of gills. The 

 stronger, bent chsetse present in the first three notopodia of the Scotia Bay specimen 

 are evidently homologous with the much stronger chsetse of the first segment of 

 S. minutus, and the three other types of chsetae present in the first notopodium of 

 the Scotia Bay specimen have their homologues in the corresponding notopodium 

 of S. minutus. These agreements in structure show that the Scotia Bay specimen 

 is closely related to S. minutus, and should certainly be placed in the genus 

 Sclerocheilus as a new species, for which I propose the name S. antarcticus. 



Observations on Sclerocheilus pacificus J. P. Moore. 



Only two species of Sclerocheilus have hitherto been described — namely, 

 S. minutus, the chief external characters of which have been already stated, and 

 S. pacificus J. P. Moore, 1909, from Monterey Bay, California. By the courtesy of 



* Since this was written the sense-organs have been briefly described by M. and Mme. Dehorne in Arch. Zool. 

 Exper., tome liii (1913), p. 72. 



