AKENICOLA MARINA. 59 



describes the different pigments of the group, viz. a yellow lipochrome and a black 

 pigment, and he thinks the latter may be a modification of the former. 



After an exhaustive inquiry into the anatomy of the Arenicolidse, Gamble and 

 Ash worth (1905) find that the genus Arenicola may be divided into two sections, the first 

 including A. marina, A. Glaparedii, and A. cristata, characterised by a well-marked pro- 

 stomium, a well-developed brain with anterior and posterior cerebral lobes, the presence 

 of six pairs of nephridia in segments four to nine, or five pairs in segments five to nine, 

 and the absence of gills and feet in the posterior region. The second section comprises 

 A. branchialis and A. ecaudata, with simple conical non-lobate prostomium and com- 

 misural brain, and the continuation of the gills and setigerous sacs to the tip of the tail. 



Ashworth (1912) includes Branchiomaldane in this family, and points out its dis- 

 tinction from Arenicola, such as the presence pf only two rings in each branchial segment 

 instead of five as in Arenicola. The nephridia are two on each side, and the form is 

 hermaphrodite, with large ova. 



1. Arenicola marina, Linnxus, 1758. Plate LXXXVIII, figs. 5, 6, and 7; Plate XCIV, 

 fig. 2— young; Plate C1II, figs. 11-11 d— bristles. 



Specific Characters. — Prostomium three-lobed, the lateral sometimes exceeding the 

 median in size. Statocysts communicating with the exterior. Statoliths formed of 

 numerous foreign bodies, e.g. sand-grains, which may be coated with a chitinoid 

 investment. Nineteen setigerous segments. Thirteen pairs of gills; the first, on the 

 seventh segment (sixth bristled segment), may be reduced or suppressed. The dorsal 

 divisions of the foot in the posterior branchial region are clorso-ventral and near the 

 middle line. Six pairs of segmental organs on segments 4—9, the first being in the third 

 bristled segment. One pair of oesophageal pouches, cylindrical, club-shaped, or conical. 

 One pair of smaller, globular, or flask-shaped muscular pouches on the first diaphragm. 

 Colour greenish-brown, or velvety-greenish black, and iridescent. The Neapolitan 

 examples are rose-red and transparent. Tail a third the length of the body (Cams). 

 Many small specimens procured amongst sand near low-water mark are pale greenish- 

 yellow with red vessels and branchiaB. The anterior and posterior ends are darker. 

 Post-larval forms are known by the open statocyst with foreign statoliths, a single pair 

 of oesophageal pouches, and the small pair of segmental organs in the third setigerous 

 segment. Larval forms are polytrochus. 



Synonyms. 

 1553. Lumhricus marinus, Belon. Hist. Poiss., p. 444. 

 1602. Lugg, Carew. Survey Cornwall, p. 346. 



1638. Lumhricus marinus, Aldrovandus. De Invert., lib. 7, p. 734. 

 1684. Vermis ex arena effosus Lug dictus, Sibbald. Scotia Illust. II, pars 3, p. 34. 

 1710. Eruca marina, Sibbald. Hist. Fife and Kinross, p. 56. 



1710. Vermes marini Scolopendroides Cornubiensibus Lugs dicti, Eay. Hist. Insect., p. 46. 

 1746. Lumhricus punctis prominulis, Linnasus. Fauna Suec, p. 364, No. 1270. 

 1751. Orm, idem. Skanska Eesa, p. 315. 

 1754. Lumhricus punctis prominulis, idem. Mus. Adolph Frid., p. 92. 



