CRENELLA. 105 
Description.—Shell subquadrate or oval, short, inflated—especially anteriorly 
and between the umbo and the postero-ventral extremity ; on each side of this line 
the shell is compressed, and on the ventral side it is flattened. Hinge-margin 
relatively short; posterior margin curved, oblique; ventral long, nearly straight. 
Postero-ventral angle rounded. Umbo prominent, extending beyond the short 
anterior margin. Ornamentation consists of numerous fine regular radial ribs, 
crossed by finer concentric ribs, which are best marked on the dorsal part of the 
valves; also at intervals a few well-marked growth-lines. 
Measurements : 
(1) (2) (3) 
Length , : . 16 : 14 : 15) mm. 
Height : : ; ita : 9 2 85 ,, 
Thickness. - : 135. 1225): IL 
(1—3) all from Atherfield. 
Affinities —This is distinguished from the other Cretaceous species’ by its 
more quadrate outline. It may, perhaps, belong to the sub-genus Ihomboidella, 
Monterosato. 
T'ypes.—I have not seen the type; it came from the Hythe Beds, near Hythe. 
Distribution. —Perna-bed of Atherfield and Redcliff. Crackers of Atherfield. 
Hythe Beds near Hythe, and near Maidstone. 
Genus—LirHopomus, Cuvier, 1817. 
(‘Le Régne Animal,’ vol. ii, p. 471.) 
LirHopomus ruGosus? d@’Orbigny, 1845. Plate XVII, figs. 14a, b. 
1845. Lirgopomus ruaosus, A. d’Orbigny. Pal. Franc. Terr. Crct., vol. ii, p. 294, 
pl. ecexlvi, figs. 1—3. 
1850. _ — —_ Prod. de Pal., vol. ii, p. 166. 
1867. — — E. Guéranger. Album Paléont. de la Sarthe, p. 18, 
pl. xxiii, figs. 18—20. 
1873. — —— H. B. Geinitz. Das Elbthalgeb. in Sachsen (Paleon- 
tographica, vol. xx), pt. 1, p. 219, pl. hi, figs. 
24.—26. 
Deseription.—Shell elongate, oval, subcylindrical, dorsal and ventral margins 
nearly parallel, extremities rounded. Surface with strongly marked erowth-lines. 
Umbones not terminal. 
1 C. concentrica, Gabb; C. elegantula, Meek and Hayden; C. sericea, Conrad; C. granulato- 
cancellata (Rimer); C. inflata (Mill.). 
14 
