NUCULANA. 3 



Affinities. — The shell in N. subrecurva is more inequilateral, and more pointed 

 at the extremities, than in N. phaseolina (d'Orbigny), and the latter is ornamented 

 with concentric ribs. 



Remarks. — Phillips gave no description of this species, and his figure is an 

 outline only, but is sufficiently characteristic to enable lis to identify the form. 



Types. — I have not seen the type of N. subrecurva. An internal cast from 

 Speeton (8 mm. in length) in the York Museum is labelled as such, but it does not 

 belong to this species. The specimens figured by Gardner are in the Leckenby 

 Collection, Woodwardian Museum. 



Distribution. — Speeton Clay (D 3 and D 4) of Speeton. 



Nucolana speetonensis, sp. nov. Plate I, figs. 6 a, b, 7 a, b. 



? Nuctila ^ouilateealis, Bean MS., ron F. A. Homer. Die Verstein. d. 

 Norddeutach. Oolitligeb. (1836), p. 101, pi. vi, fig. 13. 



Description. — Valves almost equilateral, about twice as long as high, convex, 

 anterior and posterior extremities almost equally rounded. Ventral margin 

 slightly curved, almost parallel to the dorsal. Umbones nearly central, close 

 together, of moderate size, with a depression in front and behind. Surface 

 ornamented with numerous fine concentric striae. 



Measurements : 



0) (2) 



Length ... 17 .. 18 mm. 



Height 10 9-5 „ 



Affinities. — This species resembles Leda NecJceriana, Pictet and Roux, from 

 the Gault ; but in that form the umbones are larger and more widely separated, 

 and the shell appears to be less equilateral. 



JV. phaseolina, Michelin, is smaller than N. speetonensis; it is also more 

 angular posteriorly, not quite so equilateral, and apparently more coarsely 

 ornamented. 



Types. — In the British Museum, and the Museum of Practical Geology, 

 Jermyn Street. 



Distribution. — Speeton Clay of Speeton. 



Nuculana [PYoldia] scapha (iV Orbicjny), 1844. Plate I, figs. 8 a— c, 9—14. 



1844. Nucula scapua, A. d'Orbigny. Pal. Franc. Terr. Cret., vol. iii, p. 167, 



pi. ccci, figs. 1 — 3. 



1845. — — F. Forbes. Quart. Journ. Geol. Soc, vol. i, p. 245. 

 1854. Leda scapha, J. Morris. Cat. Brit. Toss., ed. 2, p. 205. 



1866. — — F.J. Pictet and G. Campiche. Foss. du Terr. Cret. de Ste. 



Croix (Mater. Pal. Suisse, ser. 4), pt. 3, 

 pp. 395, 400, pi. cxxix, fig. 2. 



