HIND : NEW CARBONIFEROUS NAUTILOIDS. 
107 
represents a cast of the interior. He figures the surface of this 
fold as being punctate, a fact which my specimen substantiates. 
I regard this species as being very rare, the specimen I now 
figure being the only one I have ever found during many years' 
work in the Carboniferous Limestone of Great Britain and Ireland. 
PERICYCLUS MINIMUS, SP. NOV. 
(Plate IV.) 
Specific characters. — Shell small, discoidal involute, expand- 
ing gently. Inner whorls almost completely concealed by the 
outer. The umbilicus is comparatively small and shallow, its 
outer margin rounded. The greatest thickness of the whorl is 
at the umbilical margin. Whorls 3, 4, strongly convex at the 
periphery, moderately so at the sides. Whorls not numerous, 
body chamber large, in one specimen occupying three-quarters of 
a whorl. The suture has not been seen. The whorl is marked 
by three or four weU-marked transverse constrictions. The 
aperture has a shallow peripheral sinus. 
The test is of moderate thickness, ornamented by numerous 
regular, rounded, transverse ribs. The ribs are thicker on the 
sides, and either bifurcate as they pass over the periphery, or a 
rib, which does not reach the sides, is interpolated. On the 
periphery the ribs have a shallow broad sinus. 
Dimensions. — Fig. 3. PI. IV., measures : — 
Greatest diameter, 22 mm. 
Breadth of body chamber, 9 mm. 
Locality. — The Carboniferous Limestone of Thorpe Cloud, 
Derbyshire. 
Observations. — A number of specimens of this species are in 
my collection, many of them much smaller than these figured 
The general character and ornament of the sheU show marked 
affinity to the Genus Pericycltis. Unfortunately, in no case is the 
suture line exposed. 
This species is very much smaller than any other referred to 
the genus. 
