BIVALVIA. 65 



from the umbones to the posterior and inferior angle, and forms a boundary to the radiating 

 posterior lines. The posterior side is not excavated or flattened, as in some other trigonal 

 species, but is rather convex. 



It occurs very rarely near to the base of the Great Oolite, in a band of hard whitish 

 argillaceous rock, but has not been found in the shelly beds. 



Locality. The southern boundary of Minchinhampton Common. 



Cardium-pes-bovis, D'Archiac. Tab. VII, fig. 4, 4«. 



Cardium pes-bovis, D'Archiac. Mem. Soc. Geol. Fr., torn, v, t. 27, f. 2, 1843. 



Testa nucleo subtriffond, convexd ; umbonibus magnis incurvis, dorso fornicato, angulo 

 obliquo, acuto carinato ; lunula magna cor data ; latere post/' co angusto, excavato ; dorso 

 lineis longitudinalibus tenuissimis perpendicularibus ornatis. 



' Shell with the nucleus subtrigonal and convex ; umbones large, incurved, dorsal 

 surface with a ridge forming an oblique and acute angle ; lunule large, cordate ; posterior 

 side narrow and excavated ; dorsal surface with longitudinal, fine, perpendicular lines. 



The large excavated lunule, fine perpendicular lines, and more erect mesial umbones, 

 distinguish this from our C. concinnum, which latter is a much smaller species. It occurs 

 very rarely in a whitish argillaceous rock near to the base of the Great Oolite. 



Height, 30 lines ; lateral diameter, 28 lines ; diameter through both the valves, 

 22 lines. 



Locality. The southern side of Minchinhampton Common. 



Cardium concinnum. Tab. VII, fig. la, b, c. 



? Cardium minutum, D'Archiac. Mem. Soc. Geol. Fr., v, t. 27, f. 4. 

 1 — pes-bovis, junior. 



Testa ovato-orbiculari, obliqud, umbonibus angulatis incurvis, latere antico rotundo 

 brevi, lunula ' parvd, latere postico compresso aut excavato, angulo obliquo obtuso carinato; 

 dorso costulis radiantibus rotundis crebris, striis concentricis decussatis. 



Shell ovately orbicular, oblique; umbones large, angulated, and curved forwards, 

 anterior side rounded, short ; lunule small, moderately excavated ; posterior side flattened 

 and excavated, bounded by an oblique and obtuse angled carina ; dorsal surface with little 

 ribs radiating, closely arranged, rounded, and decussated by regular, numerous, concentric 

 striae. 



The posterior surface is ornamented in a manner similar to the other part of the shell, 

 but so much more faintly marked that, in ordinary or not well preserved specimens, it appears 

 smooth. The general figure has a considerable resemblance to the large Cardium pes-bovis, 

 but the latter species is much higher, and more nearly equilateral. 



Height, 9 lines; lateral diameter, 10 lines; diameter through both valves, 7 lines. 



Localities. Minchinhampton Common, Bisley Common. 



9 



