264 MALACOZOA. TEOPIOPODA. LAMELLIBRANCHIATA, 



In sand, gravel, or clay, near the shore, or in deep 

 water. 



1. Venus Casina. Thick-ridged Venus. 



Shell suborbicular, moderately convex, very thick, with con- 

 centric elevated thick rather thin-edged entire ridges; the 

 frontal slope rather convex, the posterior longer, convex ; the 

 anterior impression cordate, lamelloso-striate, the posterior 

 linear-ohlong ; the margin crenate ; the colour dull white. 

 Diameter an inch and eight- twelfths. 



First found in September, 1842, by Miss Isabella Mac- 

 gillivray, in December by me, brought up from deep water off 

 Aberdeen, but only decayed valves. 



It is not uncommon on some of the Western coasts of Scot- 

 land, where it attains a diameter of two inches. The ridges 

 vary greatly in number, regularity, and thickness. 



Venus Casina. Linn. Syst. Nat. 1130. Venus Erycina, a worn 

 shell. Penn. Brit. Zool. iv. 94. PL 54. f. 48. A. Venus Cassina. 

 Mont. Test. Brit. Suppl. 47. Venus. Casina. Turt. Brit. Biv. 141. 

 PL 9. f. 1. Venus Cassina. Flexn. Brit. Anim. 446. 



2. Venus reflexa. Thin-ridged Venus. 



Shell suborbicular, compressed, rather thin, with distant 

 concentric elevated, reflexed, broad, but thin-edged entire 

 ridges ; the intervals finely striulate in a radiating manner ; 

 the frontal slope slightly concave, the posterior longer, little 

 convex ; the anterior impression cordate, obliquely lamellate, 

 the posterior linear-oblong ; the margin marked internally with 

 very small grooves and ridges ; the colour yellowish-white, 

 often faintly radiated with reddish. Diameter an inch and a- 

 half. 



This species is nearly allied to Venus Casina, from which it 

 differs in being more compressed, with the concentric ridges 

 thinner, more elevated, and reflexed, especially toward the an- 

 terior end. 



A small individual from off' Aberdeen, found by me on the 

 4th of October, 1842; a larger single valve, by M.r. Alex. 

 Murray, at Gamrie ; and a large individual in January, 1843, 

 at the Cove, by Mr. Fergusson, one of my pupils. 



Venus reflexa. Mont. Test. Brit. Suppl. 40,168. Venus reflexa. 

 Laskey, Wera. Trans. 1, 384. PL 8. f. 1. Venus reflexa. Turt. 

 Brit. Biv. 142. PL 10. f. 1, 2. Venus reflexa. Flem. Brit. Anim. 

 446. 



