1852.] LYELL — BELGIAN TERTIARY FORMATIONS. 299 



than mine, refers them. I also obtained fragments of an Astartey 

 apparently a crag species ; so that I have little doubt of the correct- 

 ness of M. de Wael's opinion, that this yellow sand represents the 

 upper crag of Antwerp. The dark clay below resembles in mineral 

 character the London clay, and contains, like it, septaria, or concretions 

 of argillaceous limestone traversed by cracks in the interior and oc- 

 curring in regular layers. The higher beds when dried are thinly 

 fissile. Although a great number of fossil shells are annually col- 

 lected by the workmen from this clay, I was scarcely able to find any 

 after a search of several hours. The only species I saw in situ were 

 NuculaBeshayesiana, a fragment of a Dent ahum, and a Shark's tooth. 

 , But I obtained more than twenty species from the labourers. 



Schelle and Boom. 



The locality of Schelle is seen from Rupelmonde, being on the op- 

 posite bank of the Scheldt (see Map, PL XVII.). Here I found a 

 mass of clay, from 50 to 60 feet thick, covered by yellow and whitish 

 sand about 6 feet thick. 



At Boom, which is on the same side of the river, the Rupelmonde 

 clay is seen about 30 feet thick, covered, as in the other localities, 

 with the yellow sand of the crag, and said to repose on whitish sand 

 full of water, called by the workmen *^ drift." The great mass of 

 clay at Boom is divided into two beds, at the point of junction of 

 which is a layer of huge septaria. The lower bed, which contains 

 balls of pyrites, is a stiffer clay, and is about 1 5 feet thick. The 

 upper is more sandy. The only fossils which I myself found wer6 

 Pleurotoma Selysii, Nucula Beshayesiana, and an Anomia ? The 

 shells are said to be dispersed through the clay. The only small 

 species obtainable from the workmen in any locality is Corhula pisum, 

 of which I saw no separate individuals, and which would I believe 

 have been neglected but for the accident of their being frequently 

 met with, aggregated together in flattened lenticular masses of py- 

 rites. I suspect, therefore, that the Bupelmonde fauna would be 

 much richer, if naturalists had not hitherto been almost entirely de- 

 pendent, like myself, for their fossil moUusca on the workmen, who 

 overlook all but the larger and more conspicuous species. 



A description of forty-three species of shells from this formation, 

 illustrated by figures of many of the most remarkable, was published, 

 in January 1837, by M. de Koninck*. 



M. Nyst has had the kindness to furnish me with a corrected list 

 of those known to him in 1851. I procured specimens of all the 

 more abundant of these, twenty-eight in number, on the spot, and 

 have compared them, with the aid of Messrs. Morris and Edwards, 

 with the very extensive collection of shells from the London Clay in 

 the possession of the last- mentioned of these gentlemen. As the clay 

 of Rupelmonde and Boom has been often regarded as contempo- 

 raneous with the London Clay, it was necessary to consult larger 



* MemMfes de TAcad. Roy. des Sciences, &c. de Bruxelles, torn, xi., Descript. 

 des coq. foss. de I'argile de Basele, Boom, Schelle, &c. 



