288 GASTEROPODA OF THE INFERIOR OOLITE. 
220. AMBERLEYA, sp.; cf. Trochus anaglypticus, Minster. Plate XXII, fig. 12. 
1844. Trocnus anacLypricus, Minster. Goldf., Petref., pl. clxxx, fig. 4. 
It must be admitted that the details of ornamentation do not tally very well 
with those of Goldfuss’s figure, though, making allowance for difference of artistic 
treatment, and of mineral conservation, there are some grounds for inviting com- 
parison. Our fossil is unique from the ‘‘ marl with green grains” at the base of 
the Humphriesianus-zone of the Sherborne district. It may be merely a sport of 
the very abundant Amb. Obornensis. 
221. AMBERLEYA BISERTA, Phillips, 1829, Section A. Plate XXII, figs. 18, 14; 
Section B, Plate XXIII, figs. 1, 2. 
1829 and 1835, Trocuus BisERtus, Phillips. Geol. Yorks, pt. 1, pl. xi, fig. 27, 3rd edit. 
(1875), p. 259. 
1884. The “Trocnus” sBisertus-group, Hudleston. Geol. Mag., dec. 3, vol. i, 
p. 248, pl. viii, figs. 9—11. 
Bibliography, §¢.—Phillips’s type was from the Dogger, and appears to have 
been lost, but the original figure leaves no doubt as to what fossilis meant. Bean 
recognised a species belonging to the same group, which in the second edition of 
Phillips’s work, p. 129, was quoted, without figure or description, as Turbo 
unicarinatus, Bean, MS., and in the third edition, p. 258, as Littorina wnicarinata, 
Bean, MS. 
We have actually in the present case four different forms to deal with. A 
form like Pl. XXII, fig. 13, was originally described by me as Littorina biserta, but 
I now consider it to be the earlier stage of Amberleya (Trochus) biserta (Pl. XXII, 
fig. 14). Those who have followed me thus far in dealing with Amberleya will be 
fully prepared to believe in the modification of the aperture from an ovate and 
almost Purpurina-like aperture (fig. 13) to a subcircular or almost trapeziform 
aperture (fig. 14). These two, then, are merely varieties of age, and constitute 
our Section A. That there is an analogous relationship between Littorina 
unicarinata (Pl. XXIII, fig. 1) and the larger form (Pl. XXIII, fig. 2) is also 
probable, though not quite so clear, owing to imperfectly preserved apertures, 
and to the slight flattening out of the smaller specimen. It might, perhaps, be 
possible to separate them specifically from the more typical forms of Amb. 
biserta, but at present it seems safer not to do so. This, then, constitutes our 
Section B, which includes the Littorina (Turbo) unicarinata of Bean. 
