CUCULL^EA. 51 



1898. Cucull^a (Idoneaeca) Counueliana, E. G. Slceat and V. Madsen. Dau- 



marks geol. Uudersog., vol. ii, 

 1». 107, pi. vi, fig. 5. 



? 2>Jon 1846. Aeca (Cucull^a) Coenueliana, A. E. Beuss. Die Versteiu. der bohm. 



Kreidefbrmat.. pt. 2, p. 13. 



Description. — Shell more or less oblong, convex, a little inequilateral. Anterior 

 border forming an angle (90° or more) with the hinge-line, gradually curving 

 toward the ventral border. Ventral border curved. Posterior border nearly 

 straight, oblique, forming a rounded angle with the curved ventral border. 

 Umbones of moderate size, close together ; no distinct carina, but the shell is 

 sharply bent along a line passing from the umbo to the postero- ventral angle ; 

 this flattened part is divided into two nearly equal parts by a narrow carina passing 

 from the umbo posteriorly ; on the right valve the carina is thread-like and 

 crenulated ; on the left valve it is less sharply defined. Area small, narrow. 

 Ornamentation consists of numerous fine concentric ribs or strige, and radial 

 ribs usually less distinct than the concentric, but well marked anteriorly. Hinge- 

 line relatively long. Central teeth transverse ; lateral teeth parallel to the hinge- 

 margin, striated. 



Measurements : 



(i) 



Length 27 



Height 22 



Thickness 19 



Affinities. — This species is closely related to G. glabra,' Parkinson (seep. 57), 

 but it never attains such large size, and its average is much smaller. It varies 

 considerably in the proportion of length to height ; in some cases the valves are 

 only a little longer than high — in this respect differing from the type. Many forms 

 are proportionately longer than is ever the case with C. glabra. The umbones are 

 less prominent and less pointed than in the latter species. Area Robinaldina, 

 d'Orbigny, differs from this species in possessing a sharply defined carina, &c. 



I am inclined to think that the three specimens from Upware (preserved in 

 the Woodwardian Museum), which were referred by W. Keeping (vide supra) to 

 G. subnana, Pictet and Roux, belong to G. Gornueliana, 



Types. — I did not find the types in the d'Orbigny Collection. 

 Distribution. — Crackers and Lower Crioceras Group of Atherfield. Bed xiv of 

 Blackgang Chine (fide Fitton). Atherfield Beds of East Shalford. ? Lower 

 Greensand of Upware. 



(2) 



(3) 



(4) 



25-5 



38 



28 mm 



21 



32 



25 „ 



20 



— 



53 



