242 CRETACEOUS LAMELLIBRANCHIA. 
Measurements : 
(1) (2) 
Length ; ; 40) : 52 mm. 
Height 32 Dia ss 
Thickness 22 17 
(1, 2) Lympne. 
Affinities —Vhis species is allied to 7. rotunda, Pictet and Roux,! from the 
Gault of the Perte-du-Rhéne and Sainte Croix, but is distinguished by its more 
rounded outline, smaller postero-dorsal area, and less distinct concentric ornament. 
It is also allied to 7’. carinifera (p. 244). 
Remarks.—Two internal casts of this species from Lympne are in the Museum 
of Practical Geology (23470, 23471); the larger agrees closely with Sowerby’s 
figure, and may perhaps be the type, but the locality given by Sowerby is Court- 
at-Street, 1} miles west of Lympne. A small, somewhat crushed example from 
the Atherfield Clay at Dover colliery probably belongs to this species. No other 
specimens have been seen. ‘The specimens recorded by Topley as 1’. carinifera 
probably belong to 7. rotundata. 
Distribution.—Hythe Beds of Lympne and Court-at-Street.’ 
TuractA Ropinanpina? (d’Orbigny), 1845. Plate XL, figs. 1—3. 
Description.—Shell oval, nearly equilateral; right valve more convex than 
the left; posterior part not quite so high as the anterior part; postero-dorsal part 
compressed. Anterior margin rounded; ventral margin moderately convex ; 
posterior margin slightly curved; postero-dorsal margin nearly straight. Umbones 
rather prominent, curved posteriorly. Surface smooth, except for growth-lines. 
Measurements : 
(1) (2) (3) 
Length . 36 ; 26 : Sy aaanaae 
Height ' 28 : 7, : OF, 
Breadth : 13 10 6 
(1) Perna-bed, (2, 3) Crackers, Atherfield. 
Remaris.—In the English specimens, which are here provisionally referred to 
1’. Robinaldina, the shell is preserved, but the examples of that species figured by 
d@ Orbigny® and by Pictet and Campiche* are internal casts, and it is consequently 
1 «Moll. Foss. Grés verts de Gentve’ (1852), p. 414, pl. xxix, fig.6. Pictet and Campiche, ‘ Foss. 
Terr. Crét. Ste. Croix’ (‘ Matér. Pal. Suisse,’ ser. 4, 1865), p. 117. 
2 Thracia Nicoleti (Agassiz) has been recorded by Morris and by Topley from the Hythe Beds of 
Hythe, but I have not seen any British examples of that species. 
3 * Pal. Franc. Terr. Crét.,’ vol. iii (1845), p. 380, pl. ccelxxii, figs. 1, 2. 
4 «Foss. Terr. Crét. Ste. Croix’ (‘Matér. Pal. Suisse,’ ser. 4, 1865), p. 114, pl. cviui, figs. 5, 6. 
