118 | 
PLAGIOSTOMA concentrica. 
TAB. DLIX.—fig. 1. 
Spec. Cuar. Elliptical, oblique, convex, ornamented 
with many longitudinal striz and a few regular 
concentric lines ; hinge-line short ; shell thin. 
A weatiy marked slender shell, whose greatest diame- 
ter is about double the least: it is most convex towards 
the beaks, which are but a little produced. 
One of the many discoveries made by R. I. Murchison, 
Ksq. in his late tour to the North of Scotland. It was 
found in a block of gray argillaceous Limestone, accom- 
anied by Ammonites, upon the beach at Ethie, near 
r » Up 
romarty. 
PLAGIOSTOMA elongata. 
TAB, DLIX.—fig. 2. 
Spec. Cuar. Obliquely elliptical, convex, costated; 
coste few, distinct, rounded ; hinge-line short. 
Syn. Plagiostoma. Mantell, Geology of Sussex, 
gel 29. ¢5 197 
Tue longest diameter of this Plagiostoma is equal to 
twice the shortest. The coste are about fifteen or six- 
teen, prominent, rounded and smooth: they produce 
undulated margins to the valves. 
An inhabitant of the Gray Chalk Marl and Upper 
Greensand. The upper figure is from a specimen found 
at Folkstone; the other from one presented in 1814 by 
Mr. Mantell, who obtained it at Hamsey. 
