128 CRETACEOUS LAMELLIBRANCHIA. 



Geinitz 1 and by Reuss 3 as C. tenuicosta. The concentric ribs and the nodular 

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

 santonensis, Muller. 3 



Bemads. — The specimens of C. cancellata 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), Boxmoor, Luton, and Wood Ditton. 



Family— CRASSATELLITID^E, Ball. 



Genus — Ceassatellites, J. F. Kriiger, 1823. 

 (' G-eschichte d. Urwelt.,' ii, p. 466.) 



CliASSATELLITES DIVISIENSIS, Sp. 110V. 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. Umbones rather prominent, curved anteriorly. Carina rounded, 

 forming a gentle curve between the umbo and the postero-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. Gueraiajeri, d'Orbigny, 4 



1 C. GeinUzii, d'Orbigny, ' Prodr. de Pal.,' vol. ii (1850), p. 239. For references to G-einitz's 

 figures see above (p. 124). 



2 ' Die Ver stein, der bohin. Kreideformat.,' pt. 2 (1846), p. 4, pi. xxxiii, fig. 16. G. corrugata, 

 Keuss, ' G-eogn. Skizzen aus Bohmen,' vol. ii (1844), p. 190 ; Grumbel, ' Abhandl. d. k. bayerisch. Akad.' 

 (Mi'mchen), vol. x (1868), p. 568. Cardita (Venericardia) bohemica, Griepenkerl, ' Senon. Konigs- 

 lutter' (' Palaeont. Abhandl.,' vol. iv, 1889), p. 58. See also C. Cuttaldiua, d'Orbigny, ' Prodr. de 

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



;i ' Mollusk. Untersen. v. Braunschweig u. Ilsede ' (1898), p. 55, pi. vii, figs. 10 — 12. 

 1 ' Pal. Franc. Terr. Cn't.,' vol. iii (1844), p. 76, pi. eclxv, figs. 1,2 ; G-ueranger, 'Album Pak'ont. 

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



