100 MOLLUSCA FROM THE GREAT OOLITE. 
B. Species with the spire depressed and mammillated. 
A. CYLINDRICI. 
CYLINDRITES CyLInDRIcus. Plate VIII, figs. 19, 19a, 4, c. 
C. Testa cylindrica, elongata, truncata; spird depressd, vel obsoletd, vertice subconcavo; 
anfractibus angulatis, anfractu ultimo margine superiore acuto. 
Shell cylindrical, lengthened, truncated; spire depressed, almost obsolete ; vertex rather 
concave ; volutions angular, the last one with the upper margin acute. 
This is the most elongated and truncated species of the group, and might easily be 
mistaken for a specimen with an imperfect spire : in well-preserved specimens the apex may 
be observed to consist of two volutions, which rise above the others, forming a mammillated 
summit; the base of the shell is much contracted and lengthened. 
Locality. It is rare, and has been found only in the “ planking” of Minchinhampton 
Common. 
CyLINpRITES EXCAVATUS. Plate VIII, figs. 17, 17a, 4. 
C. Testa cylindrica, truncata; spird inversd, apice mammillato, vertice magno profunde 
excavato; anfractibus numerosis, marginibus acutis notatis; anfractu ultimo subconvexo, 
margine superiore acuto, subcontracto; cetere note desunt. 
Shell cylindrical, truncated; spire inverted; apex mammillated, vertex large, deeply 
excavated ; whorls numerous, their upper margins acute; the last whorl somewhat convex, 
with an acute margin, and slightly curving inwards. Base not seen. 
The specimen being rather imperfect at the base prevents our ascertaining with 
exactness the length of the species, which would appear to be intermediate to C. dudlatus 
and C. Thorentez, but is certainly less elongated than the latter species ; the vertex is large 
and very deeply crateriform, the apex not rising much above the centre of the deep con- 
cavity, and not so high as the margin of the last volution, the edges of the numerous whorls 
being visible in the concavity. 
Locality. This example and a section of another are all which have been obtained ; 
they occurred in the upper series of the Great Oolite formation, a little higher than the 
hard cream-coloured limestone, and in a rock of nearly equal compactness, two miles east 
of Minchinhampton, on the road to Cirencester; the same rock, also, contains C. acutus 
and C. angulatus, but the intractable nature of the material renders it extremely difficult to 
obtain good specimens. 
