BIVALVIA. 27 



Testa convexd suborbiculari subcequilaterali, concentrice lamelloso-rugosd ; costis 

 (11 14,) convexis nodosis tubuliferis, canalibus conformibm, auriculis anterioribus sinuosis 

 hiantibus, lunuld nulld. (Goldfuss.) 



Shell convex suborbicular, nearly equilateral with concentric rugose lamellae ; costse 

 (11 14,) convex, with nodose and elevated prominent fistulous plications, interstitial 

 spaces conformable ; anterior auricles sinuated and gaping, no lunule. 



This shell is well known as a constant fossil of the upper ragstones of the Inferior 

 Oolite ; it likewise occurs occasionally in the shelly beds of the Great Oolite, and is always 

 very imperfectly preserved, most commonly, only the outer cast remaining, but it never 

 attains the dimensions of the Inferior Oolite specimens, and would seem therefore to have 

 degenerated both in size and thickness. 



Locality. Minchinhampton Common. 



(d.} LIMA CARDiiFORMis, Sow. Tab. Ill, fig. 2, 2 a. 



PLAGTOSTOMA CAKDIIFORME, Sow. Min. Con., t. 113, f. 3, 1815. 



Testa convexd, oblique ovato-orbiculari ; antice truncatd, costis crebris (circa 52 56), 

 convexis aqualibus, canalibus angustis, lineis transversis regularibus crassiusculis, lunuld 

 excavatd. 



Shell convex, oblique, ovately orbicular, anterior side truncated, costae numerous (about 

 52 56,) convex, equal, the interstitial spaces narrow, with transverse, regular, and promi- 

 nent lines, lunule excavated. 



The shell is moderately lengthened, the longitudinal always exceeding the lateral 

 diameter, the degree of convexity though varying is considerable, the diameter through both 

 the valves being about equal to two thirds of the length of the shell, the umbones are but 

 slightly curved, and the lunule is but moderately excavated, the valves are closed at their 

 anterior borders, or leave when united the least possible fissure, the hinge border slopes 

 obliquely from the umbones on each side, and the auricles are small; the umbones are but 

 slightly separated, the ligamental area being very contracted. The costae are regularly 

 rounded, and so closely arranged, as to leave the interstitial spaces deep and narrow, the 

 surface (more especially in older specimens,) are rendered rugose by the transverse striae, 

 but in this feature, and likewise in the elevation of the ribs, there is much variety, but the 

 number of the ribs is very constant, and assists to distinguish it from Lima notata, Goldfuss, 

 in which they are much less numerous, and the interstitial spaces considerably wider, and 

 the convexity of the valve is less ; in other respects there is a considerable general resem- 

 blance between the two forms. This is the most universally distributed Lima of the 

 formation, occurring in every variety of rock, whether composed of sandstone, clay, or 

 shelly limestone. 



Locality. Minchinhampton and Sapperton. 



