150 EXOGONE NAIDINA. 



De Quatrefages (1865) instituted the genus Urania for the Exogone pusilla of 

 Dujardin, 1 which he distinguished from (Ersted's species. 



1. Exogone naidina, Mag. (Ersted, 1845. 



Specific Characters. — Head bluntly conical, the fused palpi being only marked by a 

 notch dorsally, but clearly seen inferiorly. Eyes four, connate, the anterior the larger, 

 and furnished with cuticular lenses. Median and lateral tentacles short and clavate. 

 Body linear, slightly tapered anteriorly, and more so posteriorly, 2 — 3 mm. long, and with 

 19 — 35 segments; pellucid, yellowish from the intestine; terminating posteriorly in two 

 short, clavate cirri. Proboscis with a median tooth, proventriculus whitish and granular. 

 Foot with the setigerous region obliquely truncated, and bearing falcate bristles with 

 short terminal pieces furnished with a simple hook; capillary swimming-bristles in 

 male. Dorsal cirri slightly tapered ; longest in the anterior third ; ventral cirrus shorter. 

 Both were stated by M. (Ersted to be subclavate. Ova borne on the ventral surface. 



Synonyms. 

 1845. Exogone naidina, M. (Ersted. Arch. f. Nat., xi, p. 20, Taf. 2, f. 1—14. 

 1851. „ ,, G-rube. Fam. Annel., p. 62. 



1855. Syllis longiseta, G-osse. Ann. Nat. Hist., 2nd ser., xvi, p. 32, pi. iv, f. 14 — 21. 

 1865. Exogone naidina, De Quatrefages. Annel., ii, p. 33. 

 1874. „ „ Malm. Op. cit. Goteb, p. 82. 



1879. „ „ Langerhans. Zeitsch. f. w. Zool., Bd. xxxii, p. 563. 



„ „ „ Tauber. Annul. Danic., 95. 



1883. „ „ Levinsen. Yidensk. Meddel. Foren. Kjobenh., p. 244. 



1885. „ „ Cams. Fauna Medit., p. 232. 



1890. „ „ Giard. Bull. Sc. Fr. Belg., t. xxii, p. 78. 



1893. „ „ Levinsen. Yidensk. Ud. ' Hanchs/ p. 330. 



Habitat.— Weymouth (P. H. Gosse (?) ). 



This species has been entered on the responsibility of various authors who have 

 considered Gosse's Syllis longiseta as identical with it. So far as can be made out this 

 conclusion seems to be reasonable both as regards description and figures, but no oppor- 

 tunity should be lost of re-examining this interesting form. 



Magnus (Ersted first described this small Syllid from Lille Belt near Striib, and his 

 account agrees generally with that of Gosse. He shows the eggs on the ventral surface, 

 and gives an interesting description of the development of the young from the egg up to 

 the fourteenth day, when it is furnished with a median and two lateral tentacles, four 

 separate small eyqs, four bristled segments, and two anal cirri. 



The Syllis longiseta of Gosse 2 from Weymouth, for which De Quatrefages 3 constituted 

 the genus Gossia, is a bud with long swimming-bristles and a head like Exogone if the draw- 

 ing and description can be relied on. The head shows three short clavate tentacles, and the 

 tips of the bristles are simple. De Quatrefages repeats his reference to Gosse's species by 

 1 ' Ann.. Sc. Nat./ 3 e ser., t. xv, p. 298, pi. v, fig. 9 and 10. 

 3 c Ann. Nat. Hist./ ser. 2, vol. xvi, p. 32, pi. iv, figs. 14—21 (1855). 

 3 < Annel./ II, p. 49. 



