CONOCARDIUM. 
29 
Bescription. — Shell small, equivalve, moderately convex, suborbicular, winged 
both in front and behind. Umbones small, direct, incurved, subproximate, not 
prominent, situate near the median line. Hinge-line long, nearly straight, slightly 
sunk below the rounded superior margin ; extending in front of the umbo into a 
small tubular rostrum which seems slightly tilted upwards. Anterior margin first 
produced to form this rostrum, then concave for a short distance, and then 
convex. Inferior margin broad and convex. Posterior margin oblique, straight, 
meeting the hinge-margin at an angle of about 60°. Anterior cordiform slope 
small, sharply bounded, about half the height of the shell, concave round the 
produced beak in its centre, and covered by a few small, low ribs, which are 
truncated superiorly by its elevated bounding-line or anterior keel, behind which 
the median region is moderately and evenly convex till it reaches the indistinct 
median keel, after which it sinks to form a concave hind wing. Surface of the 
back ornamented by seven or eight low flat ribs, bounded by elevated threads, 
and separated by similar low interspaces, which are generally bisected by a 
thread ; the whole crossed by rather numerous, elevated, raised, distant, con- 
centric threads, which are visible to the naked eye. Hind wing covered by about 
nine low, close, rounded ridges, crossed by similar threads. Posterior edge 
broadly gaping near the hinge-line. 
Size. — Length 10 mm., breadth 8 mm., depth 6 mm. 
Locality. — Lummaton. There are three small but well-preserved specimens in 
my Collection, and one in the Woodwardian Museum. 
Uemarhs. — There is no ambiguity about this distinct and beautiful little 
species. It is clearly identical with the species first described by d'Archiac and 
de Verneuil. The only difference is that in the German shell the hind wing is 
rather larger, the hind margin more concave, and the cordiform slope smaller ; but 
these points in the English shells are subject to much variation. Mr. T. Roberts 
confirms my identification. 
I can see no reason why Sandberger should have changed the name of his shell, 
as he himself identifies it with d'Archiac and de Verneuil's species ; nor can I see 
any reason for separating Barrande's G. rarum from it. In the figures of the 
Bohemian shell the front wing is not so defined, and there seems to be no 
radiating threads dividing the grooves as in the English specimens ; but these 
points are probably due to the fact that both of Barrande's specimens are small 
and young shells. 
Affinities. — Maurer's^ version of G. Villmarense difiers in having a very much 
larger anterior slope, and in some other points. 
1 1885, Maurer, ' Abhandl. Grrossh. Hessisch. Geol. Landes.,' Band i, pt. 2, p. 226, pi. ix, 
figs. 19, 19 a, 20, 20 a. 
