54 CRETACEOUS LAMELLIBRANCHIA. 
CucuLima (DicRANODONTA) DONNINGIONENSIS, Keeping, 1883. Plate X, figs. 11 a—e, 
12—14; Plate XI, figs. la, b, 2. 
18838. CuctuLnL®a ponninetonrnsis, W. Keeping. Foss., &c., Neoc. Upware and 
Brickhill, p. 152, pl. vii, fig. 9. 
Description.—Shell stout, subquadrate, rounded, a little equilateral, rather 
convex. Anterior margin rounded, uniting with the ventral in a regular curve. 
Ventral margin nearly parallel to the dorsal. Posterior truncated, slightly 
oblique, more or less curved, and forming with the ventral border a rounded angle 
usually a little less than a right angle. Umbones prominent, pointed, well 
separated; no distinct carina, but behind a line drawn from the umbo to the 
postero-ventral angle the shell is sharply compressed. Anteriorly the shell is 
gently compressed. Hinge-area broad, shorter than the length of the shell, 
usually three-fifths to four-fifths of the latter; ligament-grooves numerous, 
close-set, very regular. 
Ornamentation consists of well-marked but slightly elevated radial ribs, 
which are less distinct on the posterior slope of the shell; between these ribs are 
from two to five smaller ribs; lines of growth, usually faintly marked, occur at 
intervals. Hinge-plate large, extending ventrally along the anterior and posterior 
margins of the shell; central teeth small, transverse, becoming a little oblique 
laterally ; lateral teeth long, usually three or four at each end, curved ventrally 
oO? 
so as to be nearly parallel to the tmner border of the hinge-plate, and usually 
bifureating. No posterior adductor plate. Margins coarsely crenulate. 
Measurements-: 
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Length 3 : : : . 92 51 48 41 385 19 mm. 
Height : é : : . 49 49 45 38 30 16 ,; 
Thickness. : : : . 48 42 36 32 25 12 ,, 
Affinities.—This species appears to be closely allied to Arca Sablieri,’ Coquand, 
from the Aptian of Josa, bon, and Arcaine (Spain), but that form, so far as I am 
able to tell froin the figures and description, differs in the shell being higher and 
shorter, and in having a trellis-like ornamentation. Coquand refers the specimen 
figured by Vilanova® as Arca fibrosa, VOrbigny, to A. Sablieri, but Vilanova’s 
figure appears to represent quite a different form. 
Remarks.—This species was founded by Keeping on an external mould in a 
black grit nodule from the Lower Greensand of Upware, and that author con- 
1 «Mon. de l’étage Aptien de l’Espagne’ (1865), p. 187, pl. xiv, figs. 7, 8. 
2 J. Vilanova y Piera, ‘ Mem. geog.-ayric. de Castellon’ (1858), pl. ii, fig. 13. 
