54 CRETACEOUS LAMELL1BRANCHIA, 



CuculLjEA (Dicranodonta) donningtonensis, Keeping, 1883. Plate X, figs. 11 a— c, 

 12—14; Plate XI, figs. 1 a, b, 2. 



1883. Cuoull^a donningtonensis, W. Keeping. Foss., &c, Neoc. Upware and 



BrickhiJl, p. 152, pi. viii, fig. 9. 



Description. — Shell stout, subquadrate, rounded, a little inequilateral, 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 

 so as to be nearly parallel to the inner border of the hinge-plate, and usually 

 bifurcating. No posterior adductor plate. Margins coarsely crenulate. 



Measurements : 



Length .... 



Height .... 



Thickness .... 

 Affinities. — This species appears to be closely allied to Area Sablieri, 1 Coquand, 

 from the Aptian of Josa, Obon, and Arcaine (Spain), but that form, so far as I am 

 able to tell from 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 2 as Area fibrosa, d'Orbigny, 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 ' Mod. de l'etage Aptien de l'Espague ' (18G5), p. 137, pi. xiv, figs. 7, 8. 



2 J. Vilanova, y Piera, ' Mem. geog.-agric. de Castellou ' (1858), pi. ii, fig. 13. 



(1) 



(2) 



(3) 



(4) 



(5) 



(6) 



52 



51 



48 



41 



35 



19 mm, 



49 



49 



45 



38 



30 



16 „ 



48 



42 



36 



32 



25 



12 „ 



