PURPURINA. 89 
entire shell. Whorls about six, very angular. Posterior area flat, and forming a 
right angle with the sides, which are compressed and slightly undercut in the whorls 
of the spire. In the finer varieties (such as the specimen 5 a, b) there are from 
twenty-two to twenty-five longitudinal cost on each whorl, but these only extend 
about half way down the body-whorl. ‘These cost form a circlet of slight spinous 
nodes on the keels, and are continuous over the flat area. The spiral ornamentation 
is similar to that of P. elaborata, and is not traceable over the flat area. 
The aperture is ovate and relatively small; the pillar is short, and slightly 
reflexed, producing a broad and extremely shallow trough. Umbilical slit faint. 
Specimens showing a bolder character of ornamentation are figs. 5c, d, 5e, f. 
Some of these have seven whorls. In the proportions and general shape of the 
whorls these do not differ materially from what has been already described; the 
ornamentation is simply coarser. In a large series every gradation may be seen. 
Relations and Distribution.—In the character of its ornamentation, and in the 
rectangular outline of the whorls, there is considerable similarity between this 
species and P. elaborata; but the spire is higher, the shell less tumid, and the 
aperture somewhat more restricted. 
In England P. bellona is most abundant in the Parkinsoni-zone of Burton 
Bradstock and that district, where some specimens occur with a higher spire than 
any shown on the accompanying plate. It also occurs in the Cadomensis-bed at 
Oborne. Specimens from the Upper Division in the Cotteswolds may, perhaps, 
belong here, but their condition is seldom good enough for specific determination. 
5. Porpurtna peitona, D’Orbigny, var. pacopa. Plate I, figs. 7 a, b, c. 
1858. Cf. Quenstedt, Der Jura, Turbo serratus, p. 485, T. 65, fig. 7. 
Description : 
Length of a well-grown shell. . . 25 mm. 
Ratio of width to length 2 : = §74r2 100: 
Length of body-whorl to entire shell ‘ . 60: 100. 
Spiral angle : : 68°. 
The spiral angle is wider than in the more typical form. ‘The posterior area of 
the whorls slopes outwards towards the keel, and then curves upwards before 
falling over, and the ornamentation on the keel is highly nodular. 
Distribution.—P, of Burton Bradstock Cliff (p. 31) contains this form. 
Another variety with sloping whorls (see PI. I, fig. 9 a, 6) is from the Cadomensis- 
bed at Oborne. This resembles the figure of a Dundry specimen given by Tawney 
12 
