ON A NEW SPECIES OF SCLEROCHEILUS. 419 



The two known species may be separated thus : — 



1. Stronger chaetae present in first notopodium only ; the segment which bears the 

 first neuropodial cirrus varies from the 25th to the 31st . S. minutus, p. 419. 



2. Stronger chaetae are present in the first, second, and third notopodia, but are 

 not so proportionately stout as in minutus ; the first neuropodial cirrus is present on 

 the 18th to the 21st segment . . . . . S. antarcticus, p. 421. 



Sclerocheilus minutus Grube, 1863. 



Grube, Arch. f. Naturg., Jahrg. xxix, Bd. i (1863), p. 50; Taf. v, fig. 3 (Lussin piccolo, Crivizza, 



Neresine, all on Lussin Island, Adriatic). 

 Grubs, Die Insel Lussin und ihre Meeresfauna, Breslau, 1864, p. 85 (Neresine, Crivizza, Cigale). 

 Grube, Abhandl. Schles. Ges., Naturw. AM. (1868), 1869, pp. 105, 127 (Saint- Vaast). 

 Grube, 46 Jahresber. Schles. Ges. (1868), 1869, p. 67 (note on cirri). 

 Ashworth, Quart. Journ. Micr. Sci., vol. xlv (1901), pp. 293, 297. 



Dehornb, A. et L., Arch. Zool. Exper., tome liii (1913), p. 61 (Le Portel, near Boulogne). 

 M'Intosh, Ann. Mag. Nat. Hist., ser. 8, vol. i (1908), pp. 380, 381 (Guernsey, Herm). 

 Marine Biol. Assoc, Journ. Mar. Biol. Assoc, N.S., vol. vii (1904), p. 231 (Plymouth). 

 Marion efc Bobretzky, Ann. Sci. Nat., ser. 6, tome ii (1875), p. 86 (Gulf of Marseilles). 

 Marion, Ann. Sci. Nat. Zool., ser. 6, tome viii (1879), Art. No. 7, p. 5 (off Marseilles). 

 Pruvot, Arch. Zool. Exper., ser. 3, tome iii (1895), p. 643 (Banyuls) ; op. cit., tome v (1897), p. 16, 



" Catal. des Invert^bres, etc. " (Brittany ; Gulf of Lyons). 

 Saint-Joseph, Ann. Sci. Nat. Zool., ser. 7, tome xvii (1894), p. 103 (Dinard and Saint-Malo) ; op. cit., 



ser. 8, tome v (1898), p. 213 (Saint- Vaast) ; op. cit., tome x (1899), p. 164 (Paimpol); op. cit., 



ser. 9, tome iii (1906), pp. 147, 230 (Cannes). 



A Sclerocheilus bearing in the first notopodium — (l) stout but straight, tapering 

 chaetse ; (2) very strong chaetae curved at their tips ; (3) slender capillary chaetae. 

 Stout chaetae are not present in any of the succeeding notopodia or in the neuropodia, 

 the armature of which consists only of slender, capillary chaetae and furcate chaetae. 

 Neuropodial cirri appear about the 27th segment (rarely anterior to this, and in 

 some specimens not until the 31st segment), and are present in all the succeeding 

 chaetiferous segments (except in one or two of the last formed). 



Historical Account. — S. minutus was described by Grube from specimens 

 collected by him on the shores of the island of Lussin, in the Adriatic. He, however, 

 mistook the dorsal for the ventral surface. The generic name is based on another 

 misconception, for the two dark plates described by Grube (" subtus ad os laminis 2 

 nigris corneis tricuspidibus armatus ") as horny and on the ventral side of the head- 

 lobe are the eyes which are situated on the dorsal side of the prostomium. The rest 

 of the description and the figures are admirably clear, and the species was so well 

 defined by Grube that subsequent workers have had no difficulty in recognising it 

 when it came into their hands. Grube also, with his usual insight, recognised the 

 close affinity of his new genus with Scalibregma. 



