CORBULA. 213 



Non 1885. Corbulamella striatula, /. Bi/hm. Verhandl. d. nat. Vereines d. preuss. 



Rheinl., vol. xlii, p. 144. 

 1887. F. Freeh. Zeitschr. d. deutsch. geol. G-esellsch., 



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

 — 1888. G. Mailer. Jalirb. d. k. preussisch. geol. Land., 



fur 1887, p. 436. 

 1889. Corbula striattjla, 0. Griepenkerl. Senou. v. Konigslutter (Palseont. 



Abhandl., vol. iv), p. 69. 

 1897. A. Fritsch. Stud, im G-ebiete der bohm. Kreide- 



format., vi, Chlomek. Schicht., p. 64, 

 fig. 83. 

 1901. Corbtjlamella striatula, F. Sturm. Jahrb. d. k. preussisch. geol. Land., 



fur 1900, vol. xxi, p. 88. 



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

 posteriorly, inequilateral, slightly inequivalve. Anterior and ventral margins 

 rounded. Posterior margin short, obliquely truncated. Umbones broad, 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) (2) (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 G. neocomiensis, d'Orbigny, 1 by 

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

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

 C. laevis, Maas, is identical with C. striatula. Another form which appears to be 

 closely allied is G. neverisensis, de Loriol, 2 from the Grault 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 considerably stronger, but in others the difference 

 is not so great. 



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

 vol. ii (1850), p. 76. 



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



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