PLATE XI. 
SILURIAN SPECIES. 
Fie. 
1—13. WVeristella tumida, Dalman. Fig. 1, a very large example from Wenlock Lime- 
stone, Dudley. Fig. 2, after original example of Atrypa 
tenuisiriata, Sow. (Sil. Syst.,’ pl. xn, fig. 3.) Wenlock 
Limestone, Malvern Hills. Mus. Geol. Soc., London. 
Fig. 3, a specimen with hardly any apparent sinus or fold. 
Collection of Mr. E. Holler. [I am much indebted to 
this gentleman for the kind loan of this and other speci- 
mens. Figs. 4, 5, 8, and 9, a series of variations in 
shape and age, from Wenlock Limestone, Dudley, and 
Rushall Canal, near Walsall. Fig. 6 is from Wenlock 
Limestone, Malverns. Mus. Geol. Survey, London. Fig. 
10, interior surface of ventral valve; Dudley. Fig. 11, in- 
terior surface of dorsal valve, but without spirals; Dudley. 
Fig. 12, specimen showing the spiral supports, from a 
very interesting example found by Mr. R. Gibbs, in 
the Wenlock Limestone of May Hill, and presented by 
him to the Mus. of Geol. Survey, London. Fig. 13, 
internal cast of ventral valve, showing muscular impres- 
sions in relief. In the same Museum; from the Upper 
Caradoc beds, Huntley Hill (?). 
