AST ARTE . 



a third very minute one is placed just below the indistinct 

 lateral tooth, or at the termination of the posterior external 

 depression : this is not peculiar to this Genus, but may be 

 seen in many others ; sometimes, however, it is blended 

 with the lower end of the posterior muscular impression. 

 In all bivalve shells with two muscular impressions, there 

 is a depressed line to which the mantle is attached, and 

 which extends from the upper and inner edge of one mus- 

 cular impression to the other ; this line is sometimes 

 deeply sinuated on the posterior side, but in Astarte it is 

 essentially simple and not sinuated ; we mention this, be- 

 cause we think it an important discriminating character in 

 bivalve shells. The Ligament is external. 



The recent species of Astarte are the Venus Danmo- 

 )nensis of Montagu ( Crassina Danmoniensis, Lam.) : V, 

 Scoiica, Mont, (placed also in Venus, by Lam.): V. sulcata, 

 Mont, and F. compressa, Mont. ; all these are English 

 shells, and though they undoubtedly occur in other parts 

 of Europe, they do not seem to have been much noticed ; 

 they are marine, and alJ, more or less, externally, trans- 

 versely grooved, and covered with a strong, horny, gene- 

 rally olive brown epidermis : another has been dredged 

 from the bottom of Lancaster Sound ; in this, the urabones 

 are deeply eroded where they have been deprived of their 

 epidermis, but all the specimens we have seen have been 

 long dead and are otherwise much worn, wherefore, we still 

 think the eroded umbones one of (he best discriniinating 

 characters of fresh water shells. Many fossil species occur in 

 the Crag, in the Green sand, and in the Iron shot or lower 

 Oolite ; three species from the last-mentioned stratum are 

 placed by Lamarck in his Genus C?/pricardia^ with the 

 generic character of which, however, they do not agree. 



Fig. 1 Astarte Danmoniensis. 



2 inside of the riifht-hand valve. 



3 inside of the left-hand valve. 



4 modiolaris, 



a fossil species from the inferior Oolite ; many other fossil 

 species are represented in Sowerby's Mineral Conchology. 



We cannot consider this Genus as related to Crassa- 

 tella, from which its external ligament separates it ; it 

 certainly approaches in general appearance, as well as 



E articular characters, much nearer to Cyprina, and in 

 amarck's arrangement ought to come among his Conques^ 

 tnarines. 



