302 
PALEONTOLOGY OF NEW-YORK. 
Genus LYRODESMA ( Conrad ). 
Character . “ Equivalved, inequilateral; hinge with about eight diverging prominent 
cardinal teeth, transversely striated.” 
If this description, cited from Mr. Conrad, were so altered as to include shells with a 
greater number of cardinal teeth, it would include a species which appears closely allied 
to the one described as the typical form. The form of this shell, and character of the 
diverging cardinal teeth, or crenulations, are different from Nucula, and more nearly like 
Pectunculus. I prefer, however, to place it under the Genus Lyrodesma, provisionally; 
though a better knowledge of L. plana , the typical species of the genus, may hereafter 
render it necessary to separate them. 
361. 1. LYRODESMA PLANA. 
Pl. LXXXII. Figs. 11 a, b. 
Lyrodesma plana. Conrad, Ann. Geol. Report, 1841, p. 51. 
“ Subrhomboidal, compressed ; posterior margin widely and obtusely truncated ; posterior 
basal margin rectilinear; extremity rounded.” 
I have copied the figures and description of Mr. Conrad, not having seen the shell. 
It is described in the Annual Report cited above, and also figured on a plate partially 
prepared for his report on palaeontology. 
Fig. 11 a. The right valve. 11 b. Interior of the right valve, showing the cardinal teeth. 
Position and locality. In the shaly sandstones of the Hudson-river group near Rome, 
Oneida county. 
362. 2. LYRODESMA PULCHELLA. 
Pl. LXXXII. Figs. 12 a, b, c, d. 
Slightly inequilateral, broadly oval; beaks moderately elevated ; anterior extremity 
rounded; posterior extremity scarcely truncated; hinge line gently arched, marked by 
about eight diverging teeth on the posterior side of the beak, and apparently fewer (five 
or six) on the anterior side; surface marked by fine equal concentric striae. 
This is the most beautiful shell among the bivalves of this group ; its nearly symmetrical 
form, finely striated surface, and crenulated hinge line, are sufficient to distinguish it from 
any other species. It is usually compressed, and but slightly convex; but when found in a 
perfect condition it is very convex, and even ventricose towards the umbones. 
Fig. 12 a. A specimen of the natural size, from the black slate near Watertown, Jefferson county.. 
Fig. 12 b. The same enlarged, showing the character of the crenulations. 
Fig. 12 c. A smaller specimen, from the partially altered slates near Waterford, on the Hudson river. 
Fig. 12 d. The cardinal line enlarged. 
Position and locality. This species occurs in the lower part of the group at Turin, and 
near Watertown, in the unaltered slates; and near Waterford, in the black glazed slates 
of the same group. 
