CARDITA. 123 



carina extending to the postero-ventral angle, and cutting off a steeply-sloping 

 postero-dorsal part of tlie valve. Lunule rather small, cordate, broader than long.. 



Ornamentation consists of about twenty-five radial ribs on the part of the valve 

 in front of the carina ; the ril)s are strong and rounded, but are narrower than 

 the interspaces. Both are crossed l)y regular concentric lamellre, which become 

 prominent on the rilis. On tlie postero-dorsal area the ril)S are smaller, more 

 numerous, and closer together; two of tliese ribs are rather stronger than the 

 others, and divide the area into three parts. Length 21 mm. ; h(>ight 20-.5 mm.; 

 thickness 17 mm. 



Affinities. — This species was doubtfully referred by W. Keeping to C. rotundafa, 

 Pictet and Roux, but it differs from that form by its fewer and stronger ribs and 

 more triangular outline (see p. 125). 



In form it resembles G. Dufiniana, d'Orbigny,^ bi;t the ribs on the postero- 

 dor.sal area are smaller and moi'e numerous. In this respect, and in its shorter 

 and less quadrate outline, it differs from G. neocominins, d'Orbigny.- 



Remarks. — I have seen only three examples of this species, two of which are in 

 the Sedgwick Museum, and one is in the collection of Mr. J. F. Walker. 



Distribution. — Lower Greensand of Upware and Potton. 



Cardfta, sp. Plate XVIII, fig. 6. 



A specimen consisting of the united valves from which the ventral parts are 

 missing was obtained by Leckenby from the rerna-hed of Atherficld, and is now 

 in the Sedgwick Museum. It shows some resemblance to G. iqnrarensis (see 

 above), but is more elongate and more distinctly carinate. 



Cabdita, sp. 



Two specimens of Garditn from the Hythe Beds of Maidstone are in the Museinn 

 of the Geological Society. They were examined by Edward Forbes,'* who identified 

 one with C. neocomiensis, d'Orbigny, and the other -svith C. quadrata, d'Orljigny. 

 The specimens are similar in form to those species, but their state of preservation 

 is too imperfect for satisfactory determination. 



1 'Pal. Franc. Terr. Crt't.,' vol. iii (1844), p. 88, pi. cclxviii, figs. 6— 10; Pictet and Campiche. 

 ' Foss. Terr. Cret. Ste. Croix ' (' Mater. Pal. Suisse,' ser. 4, 1866), p. 334, pi. cxxvi, figs. 4, 5. 

 - D'Orbigny, ojj. cit., p. 85, pi. cclxviii, figs. 1 — 6. 

 3 ' Quart. Jouru. Geol. Soc.,' vol. i (1845), p. 242. 



