CRANIA. 103 



49. Crania cenomanensis, B'Orbigny. Plate XII, figs. 40, 41. 



Crania cenomanensis, If Orbigny. Pal. Franc;., Ter. Cretaces, vol. iv, p. 138, pi. 524, 

 figs. 1 — 4, 1847. 

 — — Sharpe. Quart. Journ. of the Geol. Soc, vol. x, p. 193, 1853. 



Diagnosis. Shell unsymmetrical, transversely oval : lower or ventral valve thick, and 

 almost flat, attached to marine objects by a large portion of its external surface ; interiorly a 

 raised margin surrounds the shell, four principal muscular impressions occupy the posterior 

 half of the inner disk, the posterior adductor pair are large and oval, slightly produced, 

 and placed obliquely close to each other and to the cardinal edge. The anterior adductor 

 impressions are almost approximate at their base, and situated close to the centre of the 

 shell, with their outer extremities directed upwards, so that a lozenge-shaped depression 

 remains between the four large impressions above described; towards the centre of the 

 shell there likewise exists a small elongated projection, the remaining portion of the inner 

 disk exhibiting distinct imprints of the vascular system. . The dorsal or upper valve is 

 thin, conical, or patelliform ; the vertex sub-central, rough externally. The interior is 

 deep, with a thin concave border, which fits upon and over the raised margin of the 

 opposite valve, a small inner ridge surrounds the shell at a short distance from the edge. 

 The posterior adductor scars are oval and widely separate; the anterior pair are placed 

 near the centre of the valve, and in contact at their base, with their outer extremities 

 directed upwards and towards the cardinal angles of the valve. 

 Dimensions variable : length 4, width 5 ; 



,, 4J, „ 7, height 2 lines. 

 Obs. The only British specimens of this species I have been able to examine were 

 discovered by Mr. Sharpe in the Upper Green Sand or gravel, of Farringdon, and belong 

 to one upper and lower valve of two different individuals. The ventral valve (PI. XII, fig. 40) 

 is very flat, with a serpula covering a portion of its outer surface, and this is likewise the 

 first example of the attached valve hitherto discovered, M. d'Orbigny being only acquainted 

 with the dorsal one (PI. XII, fig. 41), with which Mr. Sharpe's specimen perfectly 

 agrees ; I must, therefore, dissent Avith the last-named gentleman, who considers his upper 

 valve to belong perhaps to the large chalk Crania, found at Ciply, in Belgium, termed 

 C. Parisiensis by Mr. Sharpe, 1 but which appears to me specifically distinct from the 

 species which bears that name. 



Plate XII, fig. 40. Lower valve from Farringdon, in the collection of Mr. Sharpe. 



,, fig. 40". Enlarged illustration. 



„ fig. 41. Upper valve from the same locality and collection; 41", enlarged. 



1 Quart. Journal Geol. Soc, vol. x, p. 192, 30th Nov., 1853. 



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