NUCULA. 23 
Description.—Shell oval or ovate-oblong, moderately convex, rounded an- 
teriorly and posteriorly ; ventral margin evenly curved. Umbones not prominent, 
placed posteriorly. Lunule indistinctly defined. Surface smooth, but with growth- 
lines. Hinge with numerous small teeth 
about eighteen on the anterior part, 
and nine on the posterior,—the two parts forming an obtuse angle (about 133°). 
Measurements : (1) (2) 
Length . : ‘ . 21 . . 20mm. 
Height. ‘ : . td ; i Vda. 
Thickness : 13 
5 . : } = 
Affinities.—N. obtusa is closely allied to N. ovata, Mantell; it differs from the 
latter (1) in being more oval, (2) in having the ventral margin more regularly 
curved, (3) in the umbones being usually placed more posteriorly, (4) in the 
absence of a constriction near the ventral margin, and (5) in the indistinct lunule. 
Types.—The type is in the Bristol Museum. The specimen figured by 
Gardner is in the Museum of Practical Geology, Jermyn Street. 
Distribution.—Blackdown Greensand (zones vil to x); Greensand of Haldon 
(fide Downes); Upper Greensand of Devizes and Warminster. 
> 
Nucvua impressa, Sowerby, 1824. Plate IV, figs. 5, 6a—-c, 7, ?8 a, b. 
1824. Nucuna mpressa, J. de C. Sowerby. Min. Conch., vol. v, p. 118, pl. 
ececlxxvy, fig. 3. 
? 1836. = ApicuLaTa, J. de C. Sowerby. Trans. Geol. Soc., ser. 2, vol. iv, 
p. 342, pl. xvii, fig. 10. 
1850. — Impressa, d. d’Orbigny. Prodr. de Pal., vol. ii, p. 163. 
1854. -- -— J. Morris. Cat. Brit. Foss., ed. 2, p. 217. 
21854. — ApicuLata, Morris. Ibid., p. 217. 
1866. — IMPRESSA, F. J. Pictet and G. Campiche. Foss. du Terr. Crét. de 
Ste. Croix (Matér. Pal. Suisse, ser. 4), pt. 3, p. 418, 
pl. exxix, fig. 16. 
1884. — — J. S. Gardner. Quart. Journ. Geol. Soe., vol. xl 
p. 128, pl. iv, figs. 9—12. 
Non 1846. Nucura mpressa, 4. E. Reuss. Die Verstein. der béhm. Kreideformat., 
pt. 2, p. 6, pl. xxxiv, figs. 6, 7. 
— 1867. = —  £. Guéranger. Album Paléont. du Dép. de la Sarthe, 
; p. 15, pl. xx, fig. 16. 
— 1897. — — A. Fritsch. Stud. im Gebiete der bbhm. Kreideformat. 
vi. Die Chlomeker Schichten, p. 56, 
fig. 61. 
Description.—Shell oval, rounded anteriorly, angular posteriorly ; ventral 
margin evenly curved, postero-dorsal margin slightly concave. Umbones placed 
