CONOCARDIUM. 
19 
1853. Caedittm clatheattjm, Steininger. Greogn. Beschr. Eifel, p. 51. 
1854. CoNOCAKDitrM AiiFORME, Morris (pars). Catal. Brit. Foss., p. 194. 
1871. — Ohioense, Meek. Proc. Acad. Nat. Sci. Philad., p. 8. 
1876. — CLATHEATUM, F. A. Bomer. Lethsea Pal., pi. xxix, figs. 4, 4 a. 
1884. — ALiEOEME, Clarke. Neues Jahrb. f. Min., Beil.-Band iii, 
p. 379. 
?1884. — — Tryon. Struct. Conch., p. 195, pi. cxvi, fig. 93. 
1885. — — Maurer. Abhandl. G-rossh. Hessisch. Geol. 
Landes., Band i, pt. 2, p. 225, 
pi. ix, figs. 18, 18 a. 
? 1885. — YiLLMAEENSE, Maurer. Ibid., p. 226, pi. ix, figs. 19, 19 a, 
20, 20 a. 
1888. Pletjeoehynchus alieoemis, JEtheridge. Foss. Bj-it., vol. i. Pal., p. 162. 
1889. CoNO CAEDITTM TEXATTTM, Barrois. Faun. Calc. d'Erbray, p. 167, pi. xi, 
figs. 8 a — d. 
Description. — Shell small, equivalve, slightly transverse, truncated in front but 
with a long tubular rostrum, conical behind. Umbo direct, incurved, rather pro- 
minent, subproximate, situated near the anterior side. Hinge-line long, nearly 
straight, slightly arched behind, slightly sunk below the rounded superior margin. 
Anterior margin produced to form the rostrum above, straight, and nearly perpen- 
dicular below. Inferior margin narrow and nearly horizontal, slightly convex. 
Posterior margin oblique, slightly concave, meeting the hinge-margin at an acute 
angle. Anterior cordiform slope large, extending to the antero-inferior corner, 
flatly convex, only becoming slightly concave near the springing of the beak, 
ornamented by close, low, rounded ribs, the outer of which are superiorly truncated 
by the anterior keel. Anterior keel prominent, reaching nearly to the lowest point 
of the shell. Median region rather narrow and convex, ornamented by six or seven 
coarse, prominent, high, flattened ribs, which are separated by spaces of at least 
similar width and spring from the umbo, bounded posteriorly by a more or less 
indistinct median ridge. Posterior side horizontally oblique and nearly flat, conical, 
ornamented with similar ribs springing from behind the umbo. The whole surface 
covered by numerous, rather distant, minute, raised, concentric threads, which are 
generally closer on the cordiform slope. Supero-posterior edge somewhat gaping. 
8iz6. — Length 18 mm., breadth 13 mm., depth 10 mm. 
Localities. — This shell is decidedly common at Lummaton. In my Collection 
there are thirty specimens, in the British Museum three specimens, in the Torquay 
Museum two specimens, and in the Woodwardian Museum three specimens. From 
Wolborough there are three specimens in Mr. Yicary's Collection, five in the 
Museum of Practical Geology, and one in the Torquay Museum. 
BemarJcs. — Although these shells are so common, their specific limits are not 
very easy to define, as they show considerable variation in shape, and their orna- 
mentation and structure seem peculiarly liable to be masked by fossilization. 
