POTEEIOCERATID^. 
261 
cannot be accurately given, as the former is very imperfect in all the 
specimens I have access to. The septa are comparatively numerous, 
being about | an inch apart where the diameter of the shell is 7 
inches. The siphuncle is situated about midway between the centre 
and the margin, and is inflated between the septa. The surface of 
the test is marked only by fine lines of growth. 
Bemarlcs. This species attains a very large size in the B-ed Sand- 
stone of Closeburn, Sowerby’s type from that place giving the 
following measurements : — greatest length (imperfect at both ends) 
9 inches; greatest diameter 7| inches. 
I can find nothing to separate M‘Coy’s species (P. ventricosum) 
from this one. 
Horizon. Bed Sandstone Group of the Calciferous Sandstone 
series ^ (Closeburn specimens) ; Carboniferous Limestone (No. C, 326, 
— locality unknown). 
Locality. Closeburn, Dumfriesshire. 
Well represented in the Collection, which includes Sowerby’s type, 
figured in the ^ Mineral Conchology.’ 
’ See footnote, ante, p. 121. 
