104 



was difficult to extract or expose the specimens. Moreover 

 the shells were either dissolved or, for the greater part, trans- 

 formed into crystalline calcite, and for this reason they were 

 exceedingly brittle , and the preparation of them was very 

 difficult. 



In the following account, the species that were found will 

 first be mentioned and described, and subsequently the con- 

 clusions with regard to the age and the conditions of formation 

 of these deposits will be given. Once more I must draw atten- 

 tion to the unfortunate state of preservation of the material; 

 the determinations are therefore not always so certain as could 

 be wished. 



A. Pelecypoda. 



1. Nucula similis J. Sowerby. 

 Plate III, figs. 1 a— с 

 1818. Nucula similis J. Sowerby; Mineral Conch, pi. 192, fig. 10. 

 1864. — — — ; S.Wood, Monogr. of the Eocene Bivalves 



of England. Vol. I. (Palæont. Soc.) p. 118; pi. 18, fig. 11. 



A single specimen of a Nvcida seems to belong to this 

 species. Both valves are here in their natural position, but a 

 little of the central part is missing. The outline and their whole 

 form correspond well with the descriptions of N. similis J. Sow; 

 thus the siphonal region is short, with the basal termination 

 somewhat pointed, which is said to be characteristic of this 

 species. The angle at the umbones is about 90°. The surface 

 is weathered and thereby finely and rather irregularly concentri- 

 cally furrowed, and it is also covered with radiating striae. 

 The shell itself was originally thick. 



Height 13,5 mm., length 16,5 mm. and thickness about 

 9 mm. 



Another specimen of a Nucula was found among the fossils 

 from the Coeloma-bed. It probably belongs to the same species, 



