PYGOSPIO SETICORNIS. 477 
both Sars and Grube. They are very minute translucent structures (Plate CXXXVI, fig. 
12a), somewhat conical in outline, with a long curved anterior margin most minutely ser- 
rated, the serrations readily escaping detection even under high powers. The posterior 
border is concave, and the base is convex in front, concave posteriorly (O. G. curve). 
Potts considers that the conical peristomium is primitive, and that the formation of 
the peristomial funnel is a direct adaptation to microphagous habits. The prostomium is 
a definite structure, but varies in the several species, being better developed in some than 
in others. It is better developed in P. anglicus (Fig. 174) than in P. elvote from Zanzibar. 
FAMILY SPIONIDZ. 
PYGOSPIO SETICORNIS, Cirst, 1843. Plate CX XVI, fig. 12—hook; Plate CXXXVI, figs. 10 
—10b—bristles. 
Specific Characters—Head with an elevated central ridge slightly bifid anteriorly, and 
bearing the four eyes. Peristomial areas lateral. Body typical, the branchiz arising 
on the second setigerous segment, and distinct from the dorsal lamella (Cunningham and 
Ramage). Second, fourth and following segments devoid of branchize, which again appear 
at the twelfth and several following segments, disappearing toward the posterior extremity ; 
eighth and following ventral divisions of the foot bearing only hooks. ‘Tail with four lobate 
processes. Anterior bristles stouter and more boldly curved, with a scoop-shaped lamella 
in front of them; those at the tail are nearly straight. Hooks commence on the seventh 
bristled segment, and are typical, a single tooth occurrmg above the main fang and they 
have a hood. Tubes of tough, flexible secretion, coated with sand. 
SYNONYMS. 
1780.? Nereis seticornis, O. Fabr. Fauna Greoenl., p. 306. 
1843. Spio seticornis, Girsted. Gronl. Annul. Dorsib., p. 203. 
1844, _,, im idem. Arch. f. Nat., p. 106. 
1S, og * idem. Annul. Dan. Consp., p. 40, Tab. vu, fig. 108. 
NSN 5 % De Quatrefages. Annel., t. u, p. 307. 
NSIS op 5 Mébius. Comm. wiss. untersuch. deutsch. Meere Kiel, p. 108. 
NSS, gg re Cunningham and Ramage. ‘Trans. Roy. Soc. Hdin., vol. xxxiui, p. 640, pl. xxxvu, 
figs. 4—4.B. 
1897. Pygospio seticornis, Mesnil. Bull. Soc. France et Belg., p. 85. 
1902. Spio seticornis, Leschke. Wiss. Meeres. Kiel, p. 122, pl. vi, figs. 7 and 8. 
TOTO is Skorikow. St. Petersb. Mus. Ann., xv, p. 208. 
1915. Pygospio seticorms, Allen. Journ. M, B. A., vol. x, p. 630. 
1917. s ry Southern, in hitt., 1917. 
1920. cs Klason. Polych. Oresund., p. 43, text-fig. 10, a, b, c. 
1922. =n a3 McIntosh. Ann. Nat. Hist., ser. 9, vol. ix, p. 17. 
Habitat.—In tubes in the middle and upper part of the littoral zone, in clefts of the 
rocks and under stones in the Firth of Forth (Cunningham and Ramage). In Laminarian 
roots, Blacksod Bay, dredged in Clew Bay in 7—10 fathoms, and in Bofin Harbour 
