CONCHACEA.] 



MOLLUSCA. 



91 



7. Venus Casina, pi. XXXVI, f. 15.* 



Clausina Casina, First Ed., pi. 20, f. 15;* Venus Casina, 

 Linne, p. 1130; Pennant, pi. 54, f. 48 a; Maton and Rackett, 

 p. 79, pi- 2, f. 1 ; Turton, Biv, p. 141, pi. 9, f . 1 ; Montagu, 

 Sup., p. 47 ; Fleming, p. 446 ; Forbes, p. 52 ; Venus lactea, 

 Donovan, pi. 149. 



Shell suborbicular, very thick, heavy, and rather inflated ; 

 provided with numerous, transverse, much elevated, laminar, 

 concentric ridges, subcrenulated on the posterior side ; the 

 intervening furrows with nearly obsolete, transverse striae ; um- 

 bones not prominent, acute, and turned to the anterior side, 

 beneath which is a cordiform, short, deeply denned lunule, 

 covered with longitudinal, fine striae; colour yellowish-white, or 

 pale rusty-brown; inside dull white; margin very broad, finely 

 crenated, greatly thickened on the edge, and covered with a 

 dark blackish-brown coloured, laminated epidermis. 



Found in the British Channel, off" the Isle of Man ; many 

 parts on the coasts of Ireland ; and at Caithness, Scotland. 



8. Venus keflexa, pi. XXXVII, f. 12, 13. 



Clausina refexa, First Ed., pi. 19, f. 12, 13; Venus reflexa, 

 Laskey, Wernerian Mem., I, p. 384, pi. 8, f. 1 ; Montagu, Sup., 

 p. 40 and 168; Turton, Biv., p. 142, pi. 10, f. 1, 2; Fleming, 

 p. 446. 



Shell suborbicular, rather strong, subcompressed ; umbones 

 small, considerably inflected ; beneath them an oblong, cordi- 

 form lunule, elevated in the centre, and of a reddish-brown 

 colour; posterior or cartilage side broad; whole surface covered 

 with numerous, inequidistant, transverse, thin, reflected, laminal 

 ridges, which are covered with extremely fine, decussated striae; 

 on the anterior side they are very sharp, more elevated and 

 undulated, and turn in a contrary direction to other parts, 

 sometimes with a small intervening one, irregularly disposed ; 

 the furrows are beset with numerous, nearly obsolete, longitu- 

 dinal striae, which can only be seen by the aid of a lens; colour 

 pale yellowish-brown or cream-white, with two or three inter- 

 rupted, longitudinal, reddish-brown radii, consisting of sagittate 

 spots, which point towards the umbones ; inside white ; hinge 

 with three strong teeth in both valves, the middle one slightly 

 bifid; a small tubercle situate on the posterior side of the teeth, 

 under the areola, in the right valve, with an indentation in the 

 opposite one for its reception ; margin finely crenated. 



Found in the Frith of Forth ; south coast of Devon ; and 

 Bantry Bay, Ireland. 



9. Venus fasciata, pi. XXXVI, f. 10. 



Clausina faseiata, First Ed., pi. 20, f. 10; Venus fasciata, 

 Donovan, V, pi. 170; Pennant, IV, p. 203 ; Turton, Biv., p. 

 146, pi. 8, f. 9; Fleming, p. 447 ; Forbes, p. 52 ; Maton and 

 Rackett, p. 80; Venus paphia, Montagu, p. 110. 



Shell subtriangular, strong, subcompressed ; umbones pro- 

 minent, nearly central, sharp-pointed, contiguous, and much 

 turned to the anterior side, with a considerably elongated, shal- 

 low, ovate lunule beneath them, and extremely fine, longitudi- 

 nally oblique striae ; anterior side acutely hollowed, the length 

 of the lunule, at the base of which the valves are somewhat 

 peaked ; cartilage or posterior side nearly flat, with a lancealate 

 depression ; surface plain, white, yellow, or orange, but most 

 commonly with several radiations of reddish-brown, pale lilac, 

 or rusty-brown, which are sometimes interrupted, and beauti- 

 fully mottled iu some specimens; with upwards of a dozen 



broad, flat, transverse, reflected ribs, unequal both in number 

 and breadth, being narrowed and more acute at the posterior 

 side, sometimes regular, and nearly equidistant, at others, 

 arranged in threes, or pairs, and in some instances an inter- 

 vening, narrow, sharp rib between the sets ; inside smooth, 

 glossy, white, pale flesh-colour, or lilac, sometimes with a brown 

 mark at one end; margins much thickened, and finely crenated. 

 Length a little more than seven-eighths, but more commonly 

 only six-eighths of an inch. 



Found on almost all the British and Irish coasts, particularly 

 those with a gravelly or clayey bottom. 



10. Venus ovata, pi. XXXVII, f. 11. 



Timoclea ovata, First Ed., pi. 19, f. 11; Timoclea Pennantii, 

 Leach, MSS., p. 9 ; Venus ovata, Montagu, p. 120; Pennant, 

 IV, p. 97, pi. 56, f. 56 ; Maton and Rackett, p. 85, pi. 2, f. 4 ; 

 Venus Pennantii, Forbes, p. 52 ; Cytherea ovata, Fleming, p. 

 445. 



Shell subovate, subcompressed, oblique, nearly equilateral ; 

 pale brown or yellowish, frequently mottled with rusty-brown ; 

 with strong, longitudinal, divergent ribs, crossed by fine, trans- 

 verse striae, which produce tubercular elevations on the ribs, 

 and give a beautifully cancellated appearance to the surface; 

 umbones almost central, slightly inflected, with a subcordiform 

 lunule under them, which is somewhat elevated in the centre; 

 inside glossy, white, sometimes of a pale flesh-colour, being 

 frequently pale purple in the centre of the valves ; margins 

 slightly crenated. Length varying from half an inch to three- 

 quarters. 



Found on most of the British and Irish coasts. We met with 

 a variety of this species in the estuary of the Clyde, in which 

 the longitudinal ribs were set in pairs. 



Genus 11 — Cytherea Lamarck. 



Shell equivalve, generally more or less equilateral or obtusely 

 trigonal, and transverse or ovate; smooth, or variously striated; 

 with three or more short, divergent, cardinal teeth ; and one 

 anterior, approximate, lateral tooth in both valves, situate near 

 the primary teeth ; two remote, lateral, muscular impressions, 

 united by a pallial impression, which is interrupted bv a broad, 

 transverse sinus; ligament external. 



1. Cytherea Chione, pi. XXXVII, f. 2. 



Cytherea Chione, First Ed., pi. 19, f. 2; Lamarck, V, p. 566; 

 Fleming, p. 444; Turton, Biv., p. 160, pi. 8, f. 11; Venus 

 Chione, Montagu, p. 115; Donovan, I, pi. 17; Maton and 

 Rackett, p. 84 ; Chione coccinea, Leach, MSS., p. 8. 



Shell strong, obliquely ovate, subcompressed ; covered with 

 a thick, extremely smooth, glossy, chestnut-coloured epidermis, 

 with a few concentric wrinkles ; more or less radiated with 

 deeper coloured chestnut; umbones obtuse, placed considerably 

 to one side, beneath them a strong, large, cordiform lunule; 

 inside of a glossy, bluish-white ; margins thick, rounded, with a 

 hollow betwixt them when closed; pallial impressions with a 

 very broad, transverse sinus, acuminated at the point. Length 

 three inches ; breadth three and three-quarters. 



This very beautiful shell inhabits the coasts of Dorsetshire 

 and Cornwall. Young shells are frequently of a beautiful, deep 

 rosy flesh-colour. 



