174 SPIO FILICORNIS. 



At the twenty-fifth foot (Plate XCVII, fig. 9 b) the upper lamella has diminished from 

 above downward, but still fuses with the base of the branchia. Its upper angle is rounded 

 and points upward, whilst its lower angle is also rounded off as the border runs to the 

 side of the body. The bristles are somewhat longer, and the upper "dorsal more slender. 

 The ventral lamella is narrower, with a nearly rectangular upper border, and it has winged 

 hooks (Plate CV, fig. 13), with a few slender tapering bristles. The shaft of the hook 

 dilates upward, bends backward some distance below the wings, slightly dilates, and then 

 tapers somewhat distinctly to the throat, from which the main fang comes off at more than 

 a right angle, and is rather short and sharp, the crown being occupied by a prominent 

 spike. The wings are rather long and of moderate breadth. Three or four of these 

 winged hooks make their appearance about the thirteenth foot amongst the bristles of 

 the ventral division, and they increase to five or six in the fourteenth and fifteenth feet, 

 where a considerable number of the finely-tapered bristles still occur. 



The branchia is somewhat less at the fortieth foot, whilst the superior lamella forms 

 a small, bluntly- conical process, its lower border sloping gradually to the body-wall. The 

 superior bristles are all longer and more slender, the dorsal group especially so. The 

 ventral lamella forms a narrow plate, rounded dorsally and ventrally. Six winged hooks 

 form a row with a few slender bristles, whilst interiorly two thicker curved bristles bend 

 downward. The fiftieth foot (Plate XCVII, fig. 9 c) presents a still smaller branchia, but 

 the superior lamella has increased in depth, projecting as a bluntly-clavate flap directed 

 obliquely upward from the base of the branchia, the distal (external) edge being slightly 

 hollowed in the centre. The dorsal bristles exhibit no change. The ventral lamella is also 

 deeper from edge to base, and the upper and lower ends are rounded. A row of nine winged 

 hooks occupies nearly the entire edge, the largest occurring superiorly and the least 

 ventrally in an evenly diminished series, along with a row of very fine, hair-like bristles ; 

 whilst ventrally four peculiarly modified curved bristles with slightly hooked points, as in 

 Spiophanes bombya, are situated at the extreme ventral edge of the row, the points being 

 directed downward. 



So far as can be ascertained at present, this makes the nearest approach to the Spio 

 filicomis 1 of Fabricius. It is true he does not mention the cephalic ridge and its posterior 

 papilla and other particulars, but the form is about the same length, viz. an inch, and in 

 the bluntly-conical snout, eyes, branchiae, feet, and caudal cirri it agrees. 



Spio filicomis is not common, but Malmgren's description is precise. 



The Spio filicomis of De Quatrefages 2 (1865) is (Ersted's form, not that of Fabricius, 

 and it is difficult to identify it. 



The Spio martinensis of Mesnil 3 has many points in common with this species, but in 

 others it diverges. The structure of the anal region especially differs, though it must be 



1 0. Fabricius (1780) defines it as Nereis with two long thick white tentacles, with dark bands. 

 It is similar to N. seticomis, but thicker and shorter — 1 inch long and 1 line broad. Tentacles 

 thicker than in the former (Spio seticomis) black and white aimulated; segments forty-eight, besides 

 head and tail. Longitudinal lateral groove with papilla?, and dorsal cirrus on each segment. Colour 

 greyish ; in the middle mixed with red, and with a greyish longitudinal line. The tube is linear, 

 thicker, fragile, of ample length for the animal. 



2 < Annel./ t. ii, p. 307. 



3 ' Bull. sc. Fr. et Belg./ t. xxix, p. 122, pi. vii, figs. 1—20. 



