.338 
GASTEROPODA OF THE INFERIOR OOLITE. 
the lineata-procera group are briefly stated ; the apical whorls are very similar 
in all] : 
Spiral angle ..... 12° — 15°. 
Height of whorl to width . . . 1 : 1'2. 
Length variable, say .... 70 — 80 mm. 
Shell moderately turrited, extremely smooth and destitute of ornament save 
lines of growth, but under certain conditions, exhibiting a striato-punctate struc- 
ture, sutures close, whorls very slightly constricted, and raised towards the 
posterior border where there is a faint bevilled edge. The body- whorl is some- 
times rather rugose from lines of growth. 
The very peculiar and highly subulate form (PI. XXI, fig. 1) is probably an 
extreme variety of Ps. procera. The conditions of mineralization, where the outer 
shell-layer is entirely gone, serve to disclose the striato-punctate structure in this 
specimen to a marked degree. 
Relations and Distribution. — This is the narrowest and least ornamented of all 
the Pseudomelanias of the Inferior Oolite. The long form is characteristic of the 
Mtbrchisonse-zone, and is fairly abundant at Blue Wyke. It occurs also somewhat 
rarely in the Cotteswolds, and in the “Dew-bed” at Bradford Abbas. Immature 
specimens are not easy to distinguish, but the whorls are appreciably longer in 
proportion to their breadth than those of Ps. lineata, Sow. 
A specimen of Ps. procera in the cabinet of Mr. Brodie, from the opalinus-zone 
of Buckholdt Wood, exhibits the tendency to sutural gaping in the later stage 
which is so characteristic of the species next to be described. The body-whorl 
exhibits striato-punctate structure spirally arranged. 
The variety minor (PI. XVII, fig. 9) is a shortened form which serves to 
connect with Ps. lineata. Sow. This variety probably would also include Ps. 
acicula. Desk It is rare in the ParJdnsoni-zone at Burton Bradstock. 
The Dogger varieties of Pseudomelania are repeated in the Northampton Sand 
at Duston. The prevailing form is Ps. procera, having a tendency towards the \ 
species next described. 
174. Pseudomelania bicaeinata, Wright, MS. Plate XVIII, figs. 3 a, S b, S c. 
Description : 
Spiral angle . 
Height of whorl to width 
Length of well-grown specimen, say 
12°_16°. 
1 : 1 - 2 . 
100 mm. 
I 
This is a variable shell and somewhat dimorphous. The apical whorls are 
