128 CRETACEOUS LAMELLIBRANCHIA. 



Geinitz ^ and by Reuss ^ as C. tenuicosta. The concentric ribs and the nodular 

 character which they give to the radial ribs separate G. cancellata from Veneiicardia 

 santoncnsis, Miiller.'' 



llemarlcs. — The specimens of C^. cancdlata are chiefly in the form of internal 

 and external moulds ; wax casts of the latter show the character of the ornamenta- 

 tion. In a few cases small portions of the shell are still preserved. 



Type. — From the Chalk Rock of Cuckhamsley, in the Sedgwick Museum. 



Distribution. — Chalk Rock of Cuckhamsley, Aston Hill, Chinnor Hill, Thick- 

 thorn Hill (Bledlow), Boxnioor, Luton, and Wood Ditton. 



J'timiVv/— CRASSATELLITID^, X»a«. 



Gemis — Crassatbllites, /. F. Kriiger, 1823. 

 (' Geschichte d. TJrwelt.,' ii, p. 466.) 



Ckassatellites DivisiENSis, sp. uov. Plate XIX, fig. 1. 



Description. — Shell subquadrate, very inequilateral, moderately long, convex, 

 but with flattened sides, carinate. Anterior margin regularly rounded ; ventral 

 margin nearly straight, oblique to the postero-dorsal margin ; posterior margin 

 convex, oblique, forming an obtuse angle with the postero-dorsal margin, which is 

 nearly straight. TJmbones rather prominent, curved anteriorly. Carina rounded, 

 forming a gentle curve between the umbo and the postei'O-ventral angle. 

 Posterior area moderately large, apparently not divided by a median rib. Lunule 

 deep. 



Ornamentation consists of numerous, strong, regular, concentric ribs, separated 

 by shallow furrows. On the posterior area the ribs appear to be narrower. 

 Length 45 mm. ; height 37 mm. 



Affinities. — This species shows some resemblance to G. Guerangeri, d'Orbigny,* 



1 C. Geinitzii, cVOrbiguy, ' Proclr. Je Pal.,' vol. ii (1850), p. 239. For references to Geinitz's 

 figures see above (p. 1'24). 



~ ' Die Verstein. der bohm. Kreidefomiat.,' pt. 2 (184-6), p. 4, pi. xxxiii, fig. 16. C. corrngata, 

 Ecuss, ' Geogu. Skizzen aus Biilimeu,' vol. ii (1844), p. I'JO ; Giiiiibel, ' Alilmudl. d. k. bayeriscli. Akad.' 

 (Miiuclieu), vol. x (1868), p. 568. Canlita {Venericardia) boheinica, Grit'peiikerl, ' Seiiou. KiJuigs- 

 lutter' ('Palaeont. Abhandl.,' vol. iv, 1889), p. 58. See also C. Cottaldina, i'Orhigny, ' Vrodr. da 

 Pal.,' vol. ii (1850), p. 161. 



•■' ' MoUusk. Unterseu. v. Braunschweig u. Ilsede ' (1898), p. 55, pi. vii, tigs. 10—12. 



* 'Pal. Frau9. Terr. Crct.,' vol. iii (1844), p. 76, pi. cclxv, figs. 1,2; Gucranger, 'Album Pak'ont. 

 de la Sartlie' (1867), p. 13, pi. xvi, fig. 11. 



