262 MALACOZOA. TROPIOFODA. LAME1LIBRANCHIATA. 



teeth, four depressions, and an anterior obtuse ridge. 

 Ligament external, considerably sunk by an elevation of 

 the margins. Muscular impressions rather small, sub- 

 marginal ; pallial impression invaded by a very long, ob- 

 lique tapering sinus. 



1 CytherSa exoleta. Worn Cytherea. 



Shell orbicular, subequilateral, moderately conveXj with 

 concentric regular striae, and stronger growth-lines, somewhat 

 obsolete along the middle of the valves ; the depression cor- 

 date, sublamellate, abruptly defined; inner surface dull, but 

 with the muscular impressions, oblique mark, and margins 

 glossy ; the colour yellowish-white or reddish-white, with ra- 

 diating purplish or reddish bands ; inside white. Diameter 

 two inches and a-half. 



The form varies little, but the colouring presents con- 

 siderable difference, it being sometimes uniform, without 

 bands, sometimes blotched or spotted. 



Very uncommon, occurring along the coast, in sand. I 

 have never met with it alive. 



Venus exoleta. Linn. Syst. Nat. i. 1134. Venus exoleta. Penn. 

 Brit. Zool. iv. 94. PI. 54, f. 49. A; Ed. 2. iv. 209. PI. 57. f. 3. 

 Venus exoleta. Mont. Test. Brit. 116. Cytherea exoleta. Flein. 

 Brit. Anim. 445. Cytherea exoleta. Turt. Brit. Biv. 162. PL 8. 

 f. 7. Cytherea exoleta. Lamk. Syst. vi. 572, Ed. 2. vi. 314. 



2. Cytherea lincta. Glossed Cythereea. 



Shell orbicular, inequilateral, moderately convex, with fine 

 concentric regular thin striae, more prominent at either end, 

 and a few stronger growth-lines ; the surface glossy ; the de- 

 pression cordate, striato-lamellate, abruptly defined ; the colour 

 greyish -white, without markings ; the inside dull -white. 

 About an inch and a-half in diameter. 



Closely allied to Cytherzea exoleta, but with the dorsal slope 

 longer, the surface glossy, the concentric lines finer, thin- 

 edged, and more elevated at either end. 



Young shells are ratlier longer than high, but in older indi- 

 viduals the height considerably exceeds the length. 



On the sandy coasts, common. Sometimes brought up on 

 the fishing-lines. 



Cytherea lincta. Flem. Brit. Anim. 445. Cytherea lincta. Lamk. 

 Syst. v. 573; Ed. 2. vi. 315. Venus exoleta/ Penn. Brit. Zool. IT. 

 94. PI. 56. f. 49. Cytherea sinuata. Turt^rit. Biv. 163* 



