14 CRETACEOUS LAMELLIBRANCHIA. 



Affinities. — This form was referred by Gardner to N. Cornueliana., d'Orbigny, 

 but it differs from that in (1) the lesser curvature of the ventral margin; (2) the 

 longer postero-dorsal margin ; (3) the greater ventral slope of the antero-dorsal 

 margin. It appears to me to be allied to N. simplex, Deshayes, 1 but at present I 

 am unable to speak definitely of its affinities. 



Distribution. — Claxby Ironstone (zone of Bel. lateralis) of Benniworth Haven ; 

 Lower Greensand of Potton. 



Nucula Lamplughi, sp. nov. Plate II, figs. 18 a,b, 19. 



Description. — Shell oval, relatively short, rather convex in the umbonal region, 

 but somewhat compressed and tapering anteriorly; extremities rounded. Ventral 

 margin gently curved. Umbones of moderate size. Lunule oval, not sharply 

 limited. Surface of shell smooth except for lines of growth. 

 Measurements : 



(i) (2) 



Length . . 22 . . 17 mm. 



Height . . 16 . . 13 „ 



Thickness . . 11 . . 9 „ 



Affinities. — This species is relatively shorter, more rounded posteriorly, and has 

 its lunule less distinctly limited than N. planata, Deshayes. It is relatively higher 

 in the umbonal region and tapers more anteriorly than N. ovata, Mantell. 

 Types.— In Mr. Lamplugh's Collection. 

 Distribution. — Speeton Clay (D 4) of Speeton. 



Nucula, sp. Plate II, figs. 20 a — d. 



1884. Nucula simplex, J. S. Gardner. Quart. Journ. Geo]. Soc, vol.xl, p. 129, 



pi. v, tigs. 11—13. 



Description. — Shell small, triangular, smooth, somewhat compressed. Um- 

 bones small. Apical angle small. Lunule distinct. Posterior part of shell very 



1 ' Mem. Soc. Geol. tie Franc,' vol. v (1812), pi. ix, fig. 5, p. 7. D'Orbigny, ' Pal. Franc. Terr. 

 CreV vol. iii (1843), p. 166, pi. ccc, figs. 11—15. Pictet and Campiche," Foss. du Terr. Cret. de Ste. 

 Croix " (• Mater. Pal. Suisse,' ser. 4), pt. iii, p. 407. Non Gardner,' Quart. Journ. Geol. Soc.,' vol.xl 

 (1884), p. 129, pi. v, figs. 11—13. 



