264 MALACOZOA. TROPIOPODA. LAMELLIBHANCHIATA. 



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

 water. 



1. Venus Casino,. 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-oblong ; 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. PI. 54. f. 48. A. — Venus Cassina. 

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

 PI. 9. f. 1. — Venus Cassina. Flem. 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 mai'gin 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 Mr. 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, Wern. Trans. 1, 384. PI. 8. f. 1.— Venus reflexa. Turt. 

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

 446. 



