MERISTA. 99 
1882. Merista PLEBEIA, Davidson. Brit. Foss. Brach., vol. v, pt. 1, p. 20, pl. i, 
figs. 26—29. 
1885. —_ PRUNULUM, Maurer. Abhandl. Grossh. Hessisch. Geol. Landes., 
vol. i, pt. 2, p. 167, pl. vii, figs. 11, 12. 
1886. — pureBEta, @hlert. Ann. Sci. Géol., vol. xix, p. 25, pl. ii, figs. 
25—27. 
Size.—The variation in dimensions is still greater than that given by Davidson. 
Two specimens measure—in length 13 mm., width 15 mm., and depth 7 mm.; in 
length 14 mm., width 10 mm., and depth 7 mm. 
Localities.—From Lummaton there are very many specimens in my Collection, 
twenty in the Woodwardian Museum, three in the Torquay Museum. From 
Barton there are twenty specimens in the Lee Collection of the British Museum, 
including one which was figured by Phillips as Terebratula hastata ; one in the 
Museum of Practical Geology, one in the Bristol Museum. From Wolborough 
there are four specimens in Mr. Vicary’s Collection, eight in the Museum of 
Practical Geology, and one in the British Museum. From Ramsleigh there is a 
specimen in Mr. Vicary’s Collection. 
Remarks.—The numerous specimens sent to Mr. Glass yielded to him less 
information about the interior arrangements than was expected, but since then I 
have collected some naturally fractured specimens which add a few interesting 
particulars. 
First, as to the ventral valve, it appears that the shoe-lifter process supported 
on the interior two large oblique dental plates. 
Secondly, as to the dorsal valve, some weathered specimens show on the surface 
an arrow-headed mark # of which the stem is rather longer than the barbs. Other 
natural sections show that this central line or stem is the edge of a perpendicular 
septum of some depth; while in another specimen the portions of shell lying 
between this edge and the two barbs have fallen out, leaving two adjacent 
shallow concave triangular hollows. Thus it appears that in the dorsal valve 
there is a process corresponding to the shoe-lifter process, but consisting of a 
double instead of a single fold. 
The variation in shape of this species is considerable; sometimes the beak is 
much, sometimes comparatively little incurved. It varies also in the loftiness of 
the beak, the expansion of the sides, the depth of the fold, and the distance of the 
greatest transverse diameter from the beak. The fold generally forms a broad 
simple curve, flattened in the centre, but, in a few specimens belonging to the 
shape or variety described by Sowerby as A. lacryma, it is sinuated by a central 
depression. Of this latter shape there is one specimen in my Collection and one 
in the British Museum from “ Torquay,” while in the Museum of the Geological 
Society are Sowerby’s original types. From the existence of intermediate forms 
