109 



It is rather common to find two united valves in tiieir 

 natural position. 



The Cyrena-bed: Very common. 



Occurrence. France: Cuisse-la-Motte. (Deshayes). 



8. Cryptodon cfr. unicarinatus Nyst. sp. 



Plate HI, figs. 14 a— b. 

 1835. Axinus unicarinatus Nyst, Rech, coquil. foss. d'Anvers, p. 6, pi. 1, 



fig. 22. 

 1843. Axinus angulatus Sow. pro parte; Nyst., Coquilles et polypiers 



foss. de la Belgique, pi. 141; pi. 6, fig. 13. 

 1S67. Cryptodon unicarinatus I>iYST ; v. Koenen, Das marine Mittel-Oligocän. 



p. 101; pi. 4, fig. 9. 



A somewhat imperfect specimen of a little Cryptodon has 

 been found in one of the concretions. It consists of two con- 

 nected valves, of which both, but especially the left valve, are 

 somewhat imperfect. Of the hitherto described species it most 

 resembles the Cr. unicarinatus Nyst, but it perhaps belongs 

 to a new species. The outline agrees rather well with the 

 above named Oligocène form, and is like the former rather 

 high. The most essential difference is, that the lunule in the 

 Greenland specimen is comparatively longer, more lancet-shaped, 

 and less deep, moreover the keel which runs from the umbo to 

 the posterior margin seems to be less sharp; but these diffe- 

 rences may possibly arise from the shell being somewhat worn. 

 On the surface of the shell only indistinct concentric growth 

 lines are seen. 



Height 7,5 mm., length 6,5 mm. and thickness about 

 4,5 mm. 



Also in the Cyrena-bed there has been found a single 

 specimen of a species of Cryptodon which is probably identical 

 with the species above mentioned, but unfortunately the specimen 

 is somewhat crushed and imperfect. The lunule here seems to 

 agree exactly with the lunule of Cr. unicarinatus Nyst, as it 



