PANOPEHA. 227 
usually less distinct than in the variety plicata, the lunular depression is smaller 
and shallower, the umbones broader, and the ventral margin usually more distinctly 
curved. The smaller specimens of the var. neoconiensis resemble the example 
figured by d’Orbigny, in which the anterior margin is obliquely truncated, and 
a carina extends from the umbo antero-ventrally. 
In one form (Plate XXXV, fig. 10), which in other respects resembles the 
variety meocomiensis, the anterior half of the shell is relatively more inflated, and 
the posterior part is not so high as the anterior part; this form may be known 
as P. gurgitis var.a. In addition to these forms of P. gurgitis numerous other 
modifications occur. 
Specimens from the Speeton Clay have been recorded by previous writers as 
P. neocomiensis; the examples seen are few in number and not well preserved, 
but resemble closely the smaller form of P. gurgitis var. neoconiensis (Plate XXXV, 
fig. 13). In one case the fine, radial ornamentation is shown. 
Specimens from Blackdown (Plate XXXVI, figs. 6,7) resemble the variety 
plicata from the Lower Greensand, but are somewhat less convex ; these probably 
constitute only a local variety, since examples from the Upper Greensand of Dorset 
agree in convexity and in other characters with typical forms of the var. plicata 
from the Lower Greensand. The examples from Blackdown, although few in 
number, show considerable variation; one specimen (Plate XXXVI, fig. 8), is 
much shorter than usual, and resembles d’Orbigny’s' figure of P. plicata, but 
is less convex. 
Crushed internal casts of Panopea have been found in the Chalk Marl of 
Folkestone ; they resemble P. guigitis var. plicata, but their imperfect preservation 
renders determination difficult. 
Types.—The type of P. gurgitis came from the Aptian of the Perte-du-Rhone ; 
that of P. neocomiensis from the Neocomian of Aube. The type of P. plicata 
was obtained from the Lower Greensand of Sandgate, but cannot now be found. 
The type of P. leviuseula, from the Upper Greensand of Blackdown, is in the 
Bristol Museum. 
Distribution.— Lower Greensand: Perua-bed, Crackers and Beds iv, vi, vii, x, 
xiii, and xiv of Atherfield. Perna-bed of Sandown. Ferruginous Sands of Shanklin. 
Atherfield Beds of Kast Shalford and Sevenoaks. Hythe Beds of Hythe and 
Court-at-Street. Sandgate Beds of Parham Park. Mamuinillatus Bed of Folke- 
stone. Recorded by Topley from the Atherfield Clay of Haslemere, Peasmarsh, 
Redhill, and Hythe; from the Hythe Beds of Pulborough; from the Sandgate 
Beds of Folkestone and Sandgate; and from the Folkestone Beds of Folkestone. 
? Lower Greensand of Upware. ?Speeton Clay of Speeton. Gault of Black Ven 
and Folkestone. Upper Greensand of Blackdown and Black Ven. 
1 «Pal. Franc. Terr. Crcét.,’ vol. 11 (1845), p. 337, pl. ecelvui, figs. 4, 5. 
