OF THE COUNTIES OF NORTHUMBERLAND AND DURHAM. 239 
at the base ; outer-lip deeply curved towards the slit ; slit 
long, narrow. 
In Magnesian-limestone ; common. Humbleton, Tunstall, 
Silksworth, Dalton-le-Dale. 
VaR. AMPULLOSA. 
Shell rather depressed, ampullose ; spire less elevated ; 
whorls rounded, convex above and below ; suture deep. 
-Rather rare. Silksworth. 
P. Sedgwickti is very distinct from the P. (H.) carinata, Sow., 
of the Mountain-limestone, to which it has been referred. The 
spire of this species is very conical, and composed of seven or 
more whorls, which are very much flattened above and which in- 
crease very gradually in size, whereas in the P. carinata the 
whorls are fewer in number, rounder in form and increase more 
rapidly. The striz of growth are also much less distinct in the 
present species. In general form it much resembles the P. Kar- 
pinskiana, of the Mountain-limestone of Russia. The specimens 
which are considered as a variety of this species differ from the 
general form in having a shorter spire and rounder whorls. 
In dedicating this neat species to Professor Sedgwick, we are 
desirous of expressing our admiration of his excellent paper “ On 
the Geological Relations and Internal Structure of the Magnesian- 
limestone,” etc., published in the Geological Transactions. This 
paper contains a more detailed and correct account of the Mag- 
nesian-limestone of this district than any other work on the same 
subject. 
Famity. Lirrorrnipa, Gray. 
9. LITTORINA, Ferrusac. 
1. L. Mancuntensts, Brown. 
Turbo Mancuniensis, Brown, Manch. Geol. Tr. 1, pl. 6, f. 
I 3k 
Turbo minuta, Brown, Manch. Geol. Tr. 1, pl. 6, f. 4, 5. 
In Magnesian-limestone; not uncommon. Tunstall, Humble- 
ton, Silksworth. 
This species varies considerably in appearance. The spiral 
