1852.] LYELL BELGIAN TERTIARY FORMATIONS. 339 



Eocene strata immediately overlying and underlying it, have suffered 

 denudation (sometimes to the depth of 20 and 25 feet), is shown in 

 the annexed diagram. 



Fig. 9. — Section at Dieghem^ seven miles N.E, of Brussels. 



1. Siliceous sand with layers of grotto-stones, 8. Nummulites Icevigatus bed, with Crania, 



E 2, Table I., or III. b. Table XII. 4. White sand, II. a, Table XII. 



2. Siliceous schist or tripoli. 5. Newer sands, 25 feet thick. 



All the peculiar characters of the Nummulite-bed, already described 

 as belonging to it round Brussels, are repeated in this quarry. It 

 may be termed a gravel-bed, with quartz-sand, pebbles, and rolled 

 fragments (generally small, but occasionally of a large size) of a rock 

 formed of aggregated remains of Nummulites l(Evigatus, which after 

 having been consolidated must have been broken up. On these 

 fragments partially rounded, and often several inches in diameter, 

 are numerous adhering shells, of the genera Ostrea, Spondylus, and 

 Crania, also Serpulce and several Bryozoa attached to pebbles or to 

 the valves of molluscs. Terehratula Kickxii likewise occurs in this 

 bed, but no univalve shells. The presence of the Crania, so rare in 

 tertiary strata, is interesting. The same shell had been observed 

 by Captain Le Hon at Etterbeek, as already mentioned, before I 

 visited Dieghem. Mr. Davidson considers this species inseparable 

 from Crania Hoeninghausii of Michelotti'*'. The shells are of the 

 same size, and, although his figures are small, they offer the same 

 characters as the Belgian shell, which, Mr. Davidson remarks, is less 

 conical than D'Orbigny's Crania cenomanensis, which it most resem- 

 bles. Whether the tertiary beds at Turin, from which Michelotti ob- 

 tained his specimen, agree in age with those of Brussels, I cannot 

 decide. 



A magnified representation of this Crania is given in PI. XVIII. 

 fig. 8, and the following description has been drawn up by my friend 

 Mr. Davidson. 



Crania Hoeninghausii, Michelotti, 1847. [PI. XYIII. fig. 8.] 

 Shell irregular, insequiA'^alve, transversely oval, slightly conical, 



* Hill of Turin. Fossiles des Terrains Miocenes de I'ltalie Septent. 1847, 

 p. 79, pi. 2. fig. 23, 24. 



