_Affinities._--In the basis being sometimes permeated towards the circumference by pores, and by the colouring (the other species in this and the next section being dirty white), _B. patellaris_ has almost as strong a claim to be ranked in the last as in the present section: in the rounded summits of the radii, and in the state of the basis, it, perhaps, shows more affinity to _B. improvisus_ than to any other species; it is, however, almost equally allied to _B. glandula_. 27. BALANUS CRENATUS. Pl. 6, fig. 6 _a_-6 _g_. B. CRENATUS. _Bruguière._ Encyclop. Method. (des Vers) 1789. LEPAS FOLIACEA, _var. a_. _Spengler._ Skrifter af Naturhist. Selskabet, b. i, 1790. ---- BOREALIS. _Donovan._ British Shells, Pl. 160 (1802-1804). B. RUGOSUS. _Pulteney_ (?) Catalogue of Shells of Dorsetshire, 1799. ---- ---- _Montagu_ (?) Test. Brit. 1803. ---- ---- _Gould_ (!). Report on Invertebrata of Massachussetts (1841), fig. 10. B. GLACIALIS (?) _J. E. Gray._ Suppl. Parry's Voyage, 1819. B. ELONGATUS (!), CLAVATUS (!), _Auctorum variorum_. _Shell white: radii with their oblique summits rough and straight. Scutum without an adductor ridge: tergum with the spur rounded._ _Hab._--Great Britain, Scandinavia, Arctic Regions as far as Lancaster Sound, in 74° 48′ N. (Mr Sutherland); Behring's Straits (Captain Kellett); United States; Mediterranean; West Indies, (Mus. Brit.); Cape of Good Hope, (Mus. Krauss). Generally attached to shells and crustacea in deep water; sometimes to ships' bottoms. Very common. _Fossil_ in glacial deposits of Scandinavia and Canada, Mus. Lyell; in the mammaliferous, and Red, and Coralline Crags, Mus. S. Wood, J. de C. Sowerby, Bowerbank; Miocene formation, Germany, Mus. Krantz.