26 
DEVONIAN FAUNA. 
Steininger,^ and of which there is a Grerman example in the British Museum, 
seems extremely similar. In that species, however, the anterior slope seems 
more concave, the anterior keel trends more forward, the median region is wider 
and more convex, and has more regular ribs, and the concentric marks are 
coarser. It therefore seems to be distinct. 
4. CoNOCAEDiUM HYSTEEicuM, ScJilotheim, sp. PL II, figs. 6, 6 a, 6 b, 7, 7 a. 
1820. BucAEDiTES HTSTEEictJS, SchlotJieim. Petrefact., p. 207. 
1822. _ _ _ Nachtr. Petref., p. 63, pi. xx, 
figs. 1 a — c. 
1830. Caedium iNVEEStTM, SoningJiaus . Jahrb. f. Min., p. 236. 
1840. — PATJCicosTATUM, Milnster. Beitr., pt. 3, p. 59, pi. xiii, fig. 2. 
1843. Pleueoehtnchus teapezoidalis, F. A. Bomer. Verst. Harzgeb., p. 22, 
pi. vi, figs. Qa — c. 
1884. CoNOCAEDiUM HXSTEEicuM, ClurTce. Neues Jahrb. f. Min., Beil.-Band iii, 
p. 379. 
Description. — Shell small, equivalve, very convex, short, more or less rounded, 
anteriorly truncated, but with a small anterior rostrum. Umbo direct, incurved, 
sub-proximate, rather prominent, situate considerably in front of the median line. 
Anterior margin horizontally produced to form the rostrum, and then becoming 
nearly perpendicular below. Inferior margin rather narrow, convex. Posterior 
margin oblique, slightly convex, meeting the hinge-line at a high angle. Hinge-line 
long, decidedly convex behind, slightly sunk below the rounded superior margin. 
Anterior cordiform slope produced, slightly concave, ornamented by low rounded 
concentric ribs, the outer of which are truncated superiorly. Anterior keel 
oblique, generally reaching the anterior margin above the lowest point of the shell. 
Median region convex, rather broad, sometimes oblique, ornamented by about 
eight ribs. Median keel not very distinct. Posterior slope well defined, 
concave. Posterior region rather convex, ornamented with seven or eight ribs. 
Conical aliform protuberance without ribs. Ribs of median and posterior regions 
large, coarse, flat, close, divided by deep furrows, and crossed by fine irregular 
and indistinct growth-lines. Gape of supero-posterior edge very large and wide. 
Size. — Length 11 mm., breadth 10 mm., depth 10 mm. 
Locality. — There are four specimens from Chudleigh in Mr. Vicary's 
Collection.' 
Bemarlcs. — There is a considerable amount of variation in the general shape 
of these specimens, which renders them rather difficult to describe specifically, 
1 1836, Steininger, ' Bull. Soe. Geol. Fr.,' vol. viii, p. 231, figs. 
