12 CRETACEOUS LAMELLIBRANCHIA. 



Family— mCTJLIDM, Gray. 



Genus — Nocula, Lamarck, 1799. 1 

 (' Mem. Soc. Hist. Nat. Paris,' p. 87.) 



1. Lower Cretaceous Species. 

 Nucttla planata, Deshayes, 1842. Plate II, figs. 11 a, b, 12 a, b, 13, 14 a, b, 15. 



1829. Nucula otata, J. Phillips (non Mantell). Geol. Yorks., pt. 1, pi. ii, 



fig. 10, p. 122. 

 1842. — planata, Q. P. Deshayes. In A. Leymerie, Mem. Soc. Geol. de 



France, vol. v, p. 7, pi. ix, figs. 3, 4. 

 1844. — obtusa, A. d'Orbigny. Pal. Franc. Terr. Cret., vol. iii, p. 163, 



pi. ccc, figs. 1 — 5 (named 2f. planata 

 on pi. ccc). 

 1858. — impressa, F. J. Pictet and E. Benevier. Foss. du Terr. Aptien 



de la Perte du Rhone, &c. (Mater. 

 Pal. Suisse, ser. 1), p. 108, pi. xv, 

 figs. 5, 6. 

 1866. — planata, F. J. Pictet and O. Campiche. Moll. Foss. du Terr. 



Cret. de Ste. Croix (Mater. Pal. 

 Suisse, ser. 4), pt. 3, pp. 404, 417, 

 pi. cxxix, fig. 7. 

 1884. — — J. S. Gardner. Quart. Journ. Geol. Soc, vol. xl, p. 126, 



pi. v, figs. 1 — 4. 



Description. — Shell oval ; short and angular posteriorly, high and rounded 

 anteriorly; ventral margin considerably curved. Postero-dorsal margin nearly 

 straight. Lunule elongate, bounded by a blunt carina. Shell depressed in front 

 of the umbones. A faint ridge extends from the umbones anteriorly. Surface 

 with lines of growth only. 



Measurements : 















(i) 



(2) 



(3) 



(*) 



(5) 



Length . 



. 27 



. 20 . 



14-5 , 



, 16-5 , 



16 mm. 



Height . 



. 17-5 



. 14 . 



9 



. 11-5 . 



•5 „ 



Thickness 



— 



, — . 



6-5 . 



— 



jj 



1 — 3 are from Speeton ; 4 and 5 from Atherfield. 



1 In the genus Nueula I regard the posterior dorsal area as the lunule, and the anterior dorsal as 

 the escutcheon, since, except in position, they agree precisely with the lunule and escutcheon of other 

 genera. In this matter I am in accord with Sylvanus Hanley (Mon. " Nuculidse," in Sowerby's 

 ' Thesaurus Conehyliorum,' vol. iii [1866], p. 147, foot-note). 



