SPIONID^. 133 



Family XXI. — SriONiM, Sars, 1861. Spiodea, Grube. 



Cephalic lobe small, with an entire incised or bilobed margin, or two psendo- 

 tentacles, eyes often present, frequently four; so-called tentacles present or absent, 

 generally largely developed. Body as a rule small, rounded, translucent; segments 

 numerous, short, an anterior one sometimes armed and distinct from the rest, bearing 

 paleae. Buccal segment nude ; proboscis slightly differentiated, and seldom extruded ; anus 

 dorsal, surrounded by cirri, or papilla?, or with a sucker. Branchise variable, simple, ligulate, 

 lanceolate, or cirriform, sometimes absent. Branchial vessels simple, lamella of the foot 

 often continued along the branchia. Feet generally biramous, lamella behind the double 

 row of bristles, which are capillary with wings. Hooks with elongated shafts and wings, 

 the tip with one or more points above the main fang. Nerve-cords with a neural canal. 



In Montagu's MS. Volume 1 (1808) in the Linnaean Society's Library, with drawings 

 by his niece, Miss E. Dorville, figures are given of two forms, under the names of 

 Pasithoe bilineata and P. carnaria, which closely resemble Nerine. Both have a pointed 

 snout like that of N cirratulus, and the colour of the former is greenish. 



Part of the forms under the Spionidae were placed by Audouin and Edwards (1834) 

 under their " Ariciens," viz. Scoloplos and Nerine, whilst Spio, Polydora, and others were 

 relegated to an appendix in company with Campontia (a larval insect). 



CErsted 3 (as in his Annulat. Danic. Consp.) included the Spionids under his Ariciae, 

 the second family of his Chsetopoda terricolina, and under his sub-division Ariciae 

 naidinse, the distinctive characters being the presence of two long tentacles ; pinnse and 

 branchiae arranged dorsally, rarely laterally ; eyes 2 — 6 or more. Small translucent 

 forms of the Aricise which approach the Naides and Lumbrici. He refers 3 to Spione 

 trioculata, which, besides bearing two frontal processes like Scolicolepis, has bifid 

 tentacles and only three eyes. It may have been an abnormal form. 



Amongst the larvae described by Krohn and Schneider 4 is one with a facetted 

 surface, but resembling an early Nerine larva. 



The representatives of this family (Spiodea) were placed by Grube (1851) under the 

 Ariciidas, after Audouin and Milne Edwards, along with the Cirratulidae and the Sphaeo- 

 doridse. 



Various Polychaat larvae were described by Busch 5 (1851), and amongst others a form 

 (Taf. viii, figs. 1 — 4) which is most nearly related to the Spionidae. The long provisional 

 bristles are in front, and about thirty segments follow. Other larvae either belong to this 

 group, or may represent those of Owenia. 



In Nerine beata, Dr. T. Williams (1858) shows a germ-mass attached to the ciliated 

 tube (Plate VIII, fig. 19) which it embraces. He, indeed, contended that the " segmental 



1 PL xix, figs. 1 and 2. 



2 < Arch. f. Naturges./ Bd. x, p. 103, 1845. 



3 Kroner's ' Nat. Tids./ Reek. 2, Bd. i, p. 413, pi. ii, fig. 10, 1844. 



4 < Du Bois Reymond's Archiv/ 1867, Taf. 13, fig. 7. 



5 'Beobacht. Anat. u. Entwickel. Seeth./ p. 65. 



