DEVONIAN FAUNAS. 285 
UNCINULUS PYRAMIDATUS (Hall). 
Plate XXIX., Wigs: 10-11: 
See, also, p. 309. 
1859. Rhynchonella pyramidata Hall, Pal. N. Y., vol. IIL., p. 229, 
pl. 82, figs. 1 a-z, 2 a-d. 
Description.—Shell subglobular or subpyramidal in form, suboval 
or subpentagonal in outline, length and breadth equal or broader than 
long. Pedicle valve depressed-convex, more or less sharply deflected 
along the postero-lateral margins, the beak rather blunt, closely in- 
curved over that of the opposite valve; the anterior margin produced 
in a lingual extension, which is bent at nearly right angles to the 
plane of the valve, the mesial sinus but slightly depressed. Brachial 
valve very gibbous toward the front, sloping with a gentle, convex 
curve from near the front margin to the beak; umbo flattened, in- 
curved under that of the opposite valve. Surface of each valve marked 
by thirteen to eighteen simple, rounded plications, which are flattened 
or slightly grooved toward the front margin. Three or four plications 
are included in the sinus and lingual extension of the pedicle valve, 
with a corresponding number on the fold of the brachial valve. The 
plications of the pedicle valve become obsolescent upon the umbo and 
do not reach the beak; those of the brachial valve become much 
fainter, but do not wholly disappear on the umbo. 
The dimensions of a nearly-perfect individual are: length, 16 mm.; 
width, 16 mm.; thickness, 16 mm. 
Remarks.—This species is most closely related to Unicinulus nucle- 
olatus, and it is quite possible that the two grade into one another. - 
Typically U. pyramidatus has somewhat coarser plications, which are 
not so egnspicuously grooved toward the front margin, and the brachial 
valve is much more elevated in front, giving it a swbpyramidal form. 
In the Coeymans limestone the species does not grow so large as in 
the New Scotland beds. It has been found in this formation only 
in the higher beds near Hainesville. 
