Review of Recent Geological Literature. 127 
right has a weak fore tooth and a strong hind tooth : there are no 
acceesory teeth. The ligament is internal, lies on a thickened platform 
behind the teeth ; pallial line entire. 
Family Carditidae. Prosocoelus, Keferstein. This is a genus known 
as yet only in the lower Devonian of the Hartz and the Rhineland. 
The shells are thick, often large, strongly convex and with a hinge 
strongly suggesting that of the recent Venericardia. The genus Trip- 
leura Sandb., is regarded a synonym. 
To the family Cardiniidae is referred with doubt a new genus Cary- 
dium, represented by two species from the lower Devonian. These are 
characterized by a very remarkable hinge structure. The left valve 
possesses a thickened hinge- plate, bearing two strong submarginal 
grooves. The right valve has two ridges which fit into these grooves. 
. Both grooves and ridges are crenulated. 
Family Megalodontidfe. Megalodus, Sowerby. Of this peculiarly 
Devonian genus, the author makes out the structure of the hinge to be 
as follows : a central tooth ; in the left valve a conical fore and a ridged 
hind lateral tooth, in the right valve a very strong fore, a weak and 
often wanting hind tooth and a ridged lateral tooth. But one species is 
described and that has commonly been known as 31. cucullatus, but 
the earlier name M. abbreviatus Schloth is preferred ; M. adolfi Clarke, 
from the Hartz is regarded a synonym. 
Family Lucinidas. Paracyclas, Hall. 7 species. 
Family Cyprinidfe. Cypricardinia., Hall. 7 species. 
Mecynodus, Keferstein. These shells, like Goniophora in exterior but 
with strongly developed hinge and lateral teeth, are not known in the 
New York Devonian, though Whiteaves has referred a Canadian shell 
thereto with doubt. 
Goniophora., Phillips. The external resemblance to Mecynodus natur- 
ally induces an association with that genus notwithstanding what 
appear to be profound differences in the structure of the hinge. The 
author does not follow Hall in associating these shells with Modiomor- 
pha but is disposed to regard them as cyprinids of degenerate hinge- 
structure. 
Sphenotiis, Hall. To this genus is referred a single species. 
Family SolenopsidaB. Solenopms, McCoy. Of this genus of elongate, 
tapering shells three species are described, one of them being identified 
with Whiteaves' Modiomorpha. attenuata, from the Devonian of Mani- 
toba. Except for this species the genus is not known in the American 
Devonian. 
Family Solenidae. Palaeosolen, Hall. These long ensiform shells, 
with subparallel margins and gaping anterior extremities, heretofore 
known only by the single American species P. siliquoidea Hall, are re- 
presented by 4 species. 
Family Grammysiidaj. Grammysia, de Verneuil. This genus is much 
more closely restricted than it was by Hall, and is applied to shells 
showing more or less distinct evidence of the transverse cincture. Hall's 
diagnosis embraced many forms similar to those here referred to Lepto- 
