CENTRONELLA OF THE ONONDAGA LIMESTONE. 
401 
Centronella alveata. 
PLATE LXI. 
Rhynchonella 1 alveata : Hail, Tenth Report on the State Cabinet, p. 124. 1857. 
“Compare Centronella hecate : Billings, Canadian Journal, May 1861. 
Shell elongate-oval or subrhomboidal; length much greater than the 
width; sloping from above the middle to the prominent beak of the 
ventral valve, the included angle being about 70°. Anterior margin 
subtruncate for about one-third the width of the shell. 
Ventral valve prominent in the middle, from a broad, undefined, abruptly 
or scarcely subangular mesial elevation : the slope thence to the sides 
below the middle is scarcely convex, and above the middle the sides 
are more convex, with a little flattened expansion close to the margin; 
the longitudinal outline gently arched; the beak prominent, erect or 
slightly arching. 
Dorsal valve, in the upper part, convex at the sides and depressed in 
the middle into a wide undefined sinus, which, below the first third 
of the length, embraces the entire width of the valve, giving it a 
trough-shaped aspect.. 
Surface smooth : shell compact, punctate. 
Length of specimen, one inch. 
This species, described by me in 1857, has so much the form and character of 
C. hecqte, Billings, described in 1861, that I can scarcely doubt the identity of 
the two ; the only difference being in the size of the specimens. 
Geological foi'mation and locality. The original specimen of this species was 
given to me many years since by Mr. W. H. Pease, as coming from the Onondaga 
limestone; but the particular locality is unknown. 
[ Paleontology IY.] 
51 
