426 THE MEDALS OF CREATION. Cuap. XI. 
which were originally described by Mr. Sowerby, as Ceri- 
thia (viz. C. funatum and C. melanoides),* but are now 
referred to the fresh-water genus, Welania; by some con- 
chologists to Potamides. At Castle Hill they are accom- 
panied by fresh-water bivalves, and leaves of dicotyledonous 
plants. 
Of the genus Rostellaria, there is a remarkable species in 
the London Clay, called 2. macroptera, from the large wing- 
like expansion of its outer lip, in adult specimens ; see Ly. 
p- 201. An- elegant Rostellaria is found in the Galt, at 
Folkestone,t (Hoss. South D. tab. xix. figs. 12, 14,) and other 
localities; and also in the Chalk Marl. 
Casts of a large ventricose, globular univalve, called 
Doxtum,} have been found in the Chalk Marl, at Clayton, 
near Hurstpierpoint, in Sussex. This species is distinguished 
by its transverse tuberculated bands; it is a very rare pro- 
duction of the lower chalk of Sussex (Min. Conch. tab. 326). 
Turbinated shells related to Zrochus, and belonging to 
several genera, occur in the Cretaceous deposits. As is the 
case generally with the univalves of this formation, but 
slight traces of the shells remain; the thin internal nacreous 
lining is sometimes found adhering to the cast. 
In the Chalk of Touraine, species of the genera Conus 
(Lign. 135, fig. 1) and Solarium (Lign. 135, fig. 2) are 
found with the shells preserved. The specimens figured, 
Lign. 135, are selected to familiarize the student with the 
difference so commonly observable, between the outer sur- 
face of the casts, and that of the shells: in both these 
fossils the shells are marked externally with lines and 
* Foss. South Downs, tab. xvii. figs. 3, 4. 
+ “This shell belongs to the recent genus, Aporrhais, and is 
related to Cerithium, not to Strombus.”— Mr. Woodward. 
} This Chalk fossil is not a Doliuwm: it is probably related to 
Ringinella incrassata (Geol. Suss. t. xix. fig. 3), one of the Tornatellide, 
a family largely developed in the chalk. 
