VENUS. 411 



curved, and the interior is of an nniforra white, with the 

 marginal crenations extremely small and very numerous ; 

 the pallial sinus, too, is sublanceolate, and is half as long- 

 again as the adjacent muscular impression. 



The species even thus restricted exhibits a remarkable 

 latitude of variation in form, sculpture, and colouring ; but 

 these varieties are inseparably connected by intermediate 

 gradations. The general contour is heart-shaped, but 

 diifers greatly from being at times produced and therefore 

 subovate, at times abbreviated, and consequently subtrian- 

 gular. The convexity, likewise, is subject to great vari- 

 ation, some examples being decidedly ventricose, whilst 

 others, being merely convex, are for Vetieres comparatively 

 compressed. In the ordinary intermediate specimens, the 

 chief swell is rather behind the subumbonal region, and the 

 chief compression, at the anterior extremity. The valves 

 are opaque, more or less solid, and almost entirely devoid 

 of lustre ; the ordinary and more typical examples are 

 variegated, upon a whitish or cream-coloured ground, with 

 extremely numerous and very fine linear zigzag markings 

 of a livid chestnut, or reddish liver colour, which not unfre- 

 quently give an appearance of crenation to the concentric 

 sculpture. The majority of individuals are adorned with three 

 more or less distinct broader or narrower rays, which are 

 never of an uniform colour, but appear mottled, being com- 

 posed of the more thickly clustered interlacements of the 

 lineation previously mentioned, which usually becomes of a 

 darker colour, and rather broader character on these parts. 

 Occasionally, and especially in the younger shells, there 

 are two white and widely separated rays, sometimes only 

 a single subposterior one, with the commencement of the 

 second visible at the umbones ; sometimes, too, both the 

 white and dark rays are present in the same individual, 



