CORBULA. 213 



Nou 1885. C0BBULAMEH.A sTRiATULA, /. BiJim. Verhaudl. d. uat. Vereiues d. preuss. 



Rheinl., vol. xlii, p. 144. 



— 1887. — — F. Freeh. ZeitscLr. d. deutscli. geol. Gesellsch., 



vol. xxxix, p. 173, pi. xii, figs. 5—8. 



— 1888. — — G. Midler. Jahrl). d. k. preussiscli. geol. Laud., 



fiir 1887, p. 436. 



— - 1889. CoRBULA STRIATULA, 0. Oriepenkerl. Senou. v. KiJuigslutter (Palseont. 



Abliandl., vol. iv), p. 69. 



— 1897. — —A. Frih-ch. Stud, im Gebiete der bohm. Kreide- 



format., vi, Cliloinek. Schicht., p. 64, 

 fig. 83. 



— 1901. CoEBULAMELLA STEiATUi.A, F. Stumi. Jalirb. d. k. prenssisch. geol. Land., 



fih- 1900, vol. xxi, p. 88. 



Description. — Shell ovate, usually mucli inflated, produced and pointed 

 posteriori)', inequilateral, slightly inequivalve. Anterior and ventral margins 

 rounded. Posterior margin short, obliquely truncated. Umbones l)road, strongly 

 incurved, with a carina extending to the postero-ventral angle and cutting off 

 a flattened postero-dorsal area. Ornamentation consists of numerous concentric 

 ribs which extend on to the postero-dorsal area, where they are narrower and more 

 distinct. 



Measurements : 



(1) (-') (3) 



Length . 6"7 . 6*0 . 5"5 mm. 



Height . 5-0 . 4-2 . 4-0 „ 



(1) Atherfield Beds, East Shalford ; (2, 3) Crackers, Atherfield. 



Affinities. — This species is distinguished from C. neocomiensi,^, d'Orbignj-,^ by 

 the smaller and more pointed posterior end. It differs from G. suhstriatula in being 

 less inequivalve and in possessing a distinct carina. WoUemann considers that 

 C. Isevis, Maas, is identical with C. striatala. Another form which appears to be 

 closely allied is G. neverisensis, de Loriol,- from the Gault of Cosne. 



Remarks. — This species varies considerably in convexity and in relative length 

 and height. The shorter, more globose, and more distinctly rostrate forms agree 

 with the type. The more elongate and less convex forms are not so numerous, 

 and although differing considerably in shape from the globose forms, yet they 

 agree with them in other respects and do not appear to be specifically distinct. 



Specimens from the Lower Greensand of Punfield resemble G. striatula, but 

 possess stronger concentric ribs — in some cases, as in the example figured (Plate 

 XXXIV, fig. 13), the ribs are consideral)ly stronger, but in others the difference 



IS not so great. 



1 'Pal. Fraue. Terr. Crct.,' vol. iii (1846), p. 457, pi. ccclxxxviii, figs. 3 — 5, and ' Prodr. de Pal.,' 

 vol. ii (1850), p. 76. 



'- • Gault de Cosne' (1882), p. 43, pi. v, figs. 23—25. 



28 



