SPIO. 



203 



No. XXXVI. 



Spio jilicornis. 



filiform, or somewhat narrowed towards the tips. Length 8'" ; 

 breadth i'". 



Nereis filicornis. Mull. Zool. Dan. Prod. no. 2640. Fabric. Faun. 



Grcenl. 307. 

 Spio filicomis, Turt. Gmel. iv. 81. Lam. Anim. s. Vert. v. 319; 2nde 



edit. V. 559. Blainv. Diet, des Sc. nat. Ivii. 441. Oersted, Annul. 



Dan. Consp. 40; Granl. Annul. Dorsibr. 51. 



Hab. The Laminarian region. 



Desc. Worm rather compressed, narrowed backwards, of a yellow- 

 ish-brown colour made dusky from the contents of the intestine, pale 

 or colourless at both ends, where it is speckled 

 with blackish dots, irregular in their position 

 and form. Head quadrate, the central lobe bifid 

 at the apex. Tentacula about one-fourth the 

 length of the body, of a straw-yellow colour, 

 cornute-like, crenulate, obtuse at the point. Eyes 

 placed between the insertions of the tentacula, 

 the anterior pair widest apart. Segments about 

 thirty in a specimen 6'" long, all nearly alike, the 

 anal one apodous, terminated with two very short 

 elliptical styles, and with a small obtuse lobe- 

 like cirrus on each side ; hence Oersted describes 

 the tail as being quadrifurcate. Feet becoming 

 gradually smaller on the segments backwards. 

 Branchial cirrus of the anterior segments longer 

 than the foot, and exceeding the diameter of the 

 body, thick and flattened, obtuse and rounded at 

 the apex, where there is a dusky spot ; the sur- 

 face clothed with vibratile cilia. The inferior 

 cirrus is shorter, rounded, and lobe-like. The 

 bristles (No. XXXVI. fig. 1 ) are all simple, and 

 collected into fan-shaped fascicles ; those of the 

 superior fascicle are shorter and stouter, divided at the apex into two 

 minute sharp claws (crotchets, fig. 2) ; those of the inferior nume- 

 rous, very slender and setaceous. 



1. Setaceous bristle. 



2. Crotchets. 



3. Elliptical bodies. 



2. Sp. seticornis, the branchial cirri of the middle segments largest, 

 disappearing towards each extremity ; antennae filiform ; segments 

 sixty-eight and upwards. Length 8-10'" ; breadth ^'". 



Altera Nereidum species. Bast. Opusc. Subs. ii. lib. ii. 134. pi. 12. f. 2. 



Nereis seticornis. Fabric. Faun. Grosnl. 306. 



Spio seticornis, Turt. Gmel. iv. 81 ; Brit. Faun. 13/. Penn. Brit. 



Zool. edit. 1812, iv. 92. Stark, Elem. ii. 138. Oersted, Annul. 



Dan. Consp. 40; Grosnl. Annul. Dorsibr. 61. Grube, Fam.Annel. 



66. 



Hab. The littoral region. 



Obs. The pairs of eyes are parallel. 



The segments are unspotted. 



