92 



MOLLUSCA. 



[CONCHACEA. 



2. Cytherea minima, pi. XXXVII, f. 3. 



Cytherea minima, First Ed., pi. 19, f • 3 ; Cyprina minima, 

 Turton, Biv., p. 137; Fleming, p. 444 ; Venus minima, Mon- 

 tagu, p. 121, pi. 3, f. 3; Maton and Rackett, p. 81. 



Shell strong, thick, suborbicular, a little compressed ; um- 

 bones prominent, acute at the points, and a little turned to 

 one side ; outer surface with broad, concentric stria; ; of a 

 delicate flesh-colour, and very glossy, with two white, diver- 

 gent, pretty broad lines, which emanate from the umbones, 

 and reach half way down the disks, like the letter V; at the 

 extremity of each line is a red streak, diverging outwards to 

 the margin ; in some specimens, however, this is wanting ; but 

 all of them have spots near the margin ; inside glossy, white ; 

 margin plain. Length a quaiter of an inch; breadth some- 

 what more. 



Inhabits the harbour of Falmouth. 



3. Cytherea minuta, pi. XXXVII, f. 4. 

 Cytherea minuta, First Ed., pi. 19, f. 4. 



Shell nearly orbicular, thick, glossy ; of a deep fawn-colour, 

 and wide-set, concentric striae; with two white lines, emanating 

 from the umbones, and diverging to the base of the valves, in 

 the form of the letter V ; inside glossy, and of a pale pink ; 

 margins smooth. Diameter three-eighths of an inch. 



I found a single specimen of this shell on the beach near 

 Dunbar, with the animal in it, but in a very decayed con- 

 dition. 



This shell differs from the preceding species, in being nearly 

 orbicular, and in the triangular lines reaching to the base. 



Genus 12 Artemis — Poli. 



Shell nearly orbicular and lenticular, externally and concen- 

 trically grooved; beaks much turned to one side, beneath them 

 a short, strongly marked, cordiform lunule; three cardinal teeth 

 in each valve, two of which are contiguous, and the other 

 divergent and broad in the right valve, cleft in the centre, to 

 receive that of the opposite valve, which is slender, with a 

 small, lateral, closely approximated tooth; pallial impression 

 with a very large, deeply defined, wedge-shaped, obliquely 

 ascending, nearly straight-sided sinus, reaching, in most species, 

 two-thirds across the valves; cartilage subexternal. 



1. Artemis exoi.eta, pi. XXXVI, f. 1, 3, 19, 20. 



Exoleta orbicularis, First Ed., pi. 20, f. 1, 3, 19, 20; Arte- 

 mis exoleta, Poli, II, p. L, pi. 21, f. 9, 10, 11; Forbes, p. 51 ; 

 Venus exoleta, Montagu, p. 116; Donovan, II, pi. 42; Maton 

 and Rackett, p. 87, pi. 3, f. 1 ; Turton, Biv., p. 1G2, pi. 8, f. 7; 

 Cytherea exoleta, Lamarck, V, p. 572. 



Shell orbicular, lentiform, strong, moderately convex ; with 

 numerous, close-set, filiform, regular, concentric striae, and 

 many well defined, hollow lines of growth ; anterior side pro- 

 vided with a nearly obsolete, longitudinal furrow; stria; on the 

 disk, and as far as the umbones, smooth and slightly depressed, 

 but thin, elevated, and sharp on the sides ; umbones small, 

 approximating, slightly produced, and much turned to one side, 

 beneath them is situated a considerably sunk, strongly defined, 

 elongated, cordiform, closely ami longitudinally striated lunule ; 

 external surface of a cream-white, yellowish-brown, or pale 

 fawn-colour, frequently with two or three very broad rays of 



rufous-brown, differing in degree of intensity in various speci- 

 mens, sometimes the rays consist of an interrupted series of 

 triangular spots, and in some instances the surface is nearly 

 covered by zigzag lilac markings; inside smooth, white, but not 

 glossy, excepting the muscular and pallial impressions ; margins 

 plain. Ordinary diameter of the shell an inch and three- 

 quarters ; but in the Irish Channel it is not unfrequently met 

 with measuring two inches and a half. 



This shell is subject to some variation in depth, and when 

 full grown the line of junction of the valves is undulated, exhi- 

 biting a considerable twist in the seam. 



A variety of this shell was found in the Frith of Forth, by 

 my friend James Gerard, Esq., of Edinburgh, with the striae 

 wide-set, elevated, and very sharp. 



2. Artemis lincta, pi. XXXVI, f. 2 and 4. 



Exoleta lincta, First Ed., pi. 20, f. 2 and 4 ; Forbes, p. 51 ; 

 Venus lincta, Pulteney, Cat. Dorset, p. 34; Venus exoleta, var., 

 Maton and Rackett, p. 87, pi- 3, f. 2; Cytherea lincta, Lamarck, 

 V, p. 573; Cytherea sinuata, Turton, Biv., p. 169, but not the 

 figure. 



Shell lentiform, nearly orbicular, slightly elongated, and mo- 

 derately thick; with numerous, very fine, filiform, close-set, 

 concentric stria;, smooth, flattened, and wide on the disk, ex- 

 tending to the umbones in the centre of the valves, elevated, 

 sharp, and sublamellar on the sides, and numerous, hollow, 

 distinctly defined lines of growth, with a longitudinal, slightly 

 hollowed furrow on the posterior sides; umbones a little pro- 

 duced, approximate, much turned to one side, beneath which is 

 a deeply defined, elongated, cordiform lunule, with exceedingly- 

 fine, obliquely longitudinal stria;; hinge line of the anterior side 

 with a long, flattened, lancealate depression, and very fine, lon- 

 gitudinally oblique striae ; external surface of a uniform pale 

 yellowish-brown, or fawn-colour, sometimes of a livid hue; 

 inside white, but not smooth, except the muscular and pallial 

 impressions, together with the entire of the broad space be- 

 neath them ; margins plain. Seldom exceeding an inch and a 

 half in length. 



This shell is distinguished from the A. exoleta, by its more 

 elongated form, and more taper shape towards the umbonal 

 region ; by the much finer stria;, being nearly double in num- 

 ber, and its uniform colour, being always devoid of radiations 

 or markings of any kind, and in the hinge line over the liga- 

 ment being flattened ; whereas the A. exoleta scarcely exhibits 

 any appearance of that character, the twist of the seam is also 

 much less in degree. It is liable to considerable variation in 

 length, and also in the depth of the valves. 



It is common on most of the British and Irish coasts. 



Turton has properly described the species, but most errone- 

 ously given a representation of its congener, A. exoleta. 



Genus 13 Cyprina — Lamarck. 



Shell ventricose, equivalvc, inequilateral, obliquely heart- 

 shaped; umbones obliquely curved anteriorly; three cardinal 

 teeth in each valve, approximated at their bases, and divergent 

 above ; with a posterior, lateral tooth, remote from the primary 

 teeth, elevated in the right valve, and receiving between it and 

 the margin, the long flat tooth of the opposite valve; external 

 surface covered by a thick, horny epidermis ; each valve with 



