THE CRETACEOUS FORMATION. 
17 
Variety y. 
Greensand, Farringdoii. 
A mutilated valve of this species, from the Coralline bed at Farringdon, exhibits 
a surface covered with longitudinal lines of punctations, much smaller than those of 
the Charing specimens. 
No. 2. Cythereis Gaultina, nobis. Tab. II, fig. 7 a — c. 
INCH. 
Length, gL 
Heiglit, Gault, Folkstone. 
Thickness, 
Carapace nearly oblong, somewhat foot-shaped. Valves depressed. Anterior ex- 
tremity rounded, edged with coarse spines ; posterior contracted, coarsely spined. 
Dorsal and ventral margins nearly straight. A little within the anterior and posterior 
margins respectively, the surface of the valve is raised into coarse, semicircular ridges, 
following the outline of the extremities. The central surface rises into a low four- 
sided pyramid. The whole surface exhibits a beautiful arrangement of slightly raised 
network ; the meshes are irregularly hexagonal, and occupied by a slight depression 
with a little central pit. The reticulations are cut across abruptly at the extremities, 
and the parietes of the meshes are there prolonged into coarse, obtuse spines. The 
hinges are slightly developed. 
This rare and pretty little species occurs only in the Gault. 
No. 3. Cythereis macrophthalma, Bosquet. Tab. II, fig. 8 a—U". 
Cypridina macrophthalma. Bosquet. 184". Ent. foss. Maestricht, p. 16, n. 10, pi. iii, 
fig. 3 a — d. 
INCH. 
Tj^no-th 
Height, gig Chalk, Norwich. 
Thickness, 
Chalk, Maestricht {Bosquet). 
somewhat oblong ; irregularly gibbous; obliquely rounded; 
posteriorly subacute. Dorsal margin more or less arched ; ventral nearly straight. The 
valve bears an irregular marginal ridge, broad and convex on the dorsal border, narrow 
or obsolete elsewhere. The central tubercle is large and irregular, extending back- 
wards. The hinges are very strongly developed. 
This species is very rare, two odd valves only being found in the Soft Chalk at 
Thorpe, near Norwich : it is described by M. Bosquet as occurring at Sichen. 
D 
