L AMELLIB RANCHI A TA. 
371 
group, in Schoharie and Otsego counties, and found in nearly all localities 
throughout Eastern and Central New York, but seldom in the softer shales in 
the western part of the State. It also occurs in the shales of the Hamilton 
group at Patterson’s creek, Va. 
Grammysia lirata. 
[ Probably the young- of Grammysia alveata. ] 
PLATE LIX, FIGS. 6-12. 
Grammysia lirata, Hall. Prelim. Notice Lamellibrancliiata, 2, p. 57 1S70. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 59, figs. 6-12. 1S83. 
A farther examination of this form, with larger collections, indicates that 
the characters upon which the species was founded may be only those belong¬ 
ing to an immature shell. 
In these forms the concentric undulations are comparatively more numerous, 
and are not so distinctly limited by the umbonal ridge. The numerous 
and characteristic concentric folds are shown in figs. 6, 7 and 10 of plate lix. 
The ridge adjacent to the escutcheon, as shown in fig. 10, is due to the vertical 
compression of the shell, and does not differ from the same part of the shell in 
G. alveata when preserved in similar conditions. The same figure shows the 
concentric undulations extending over the cardinal slope in a subdued degree, 
not limited by the umbonal ridge. In figs. 8, 9 and 11, the concentric folds 
pass over the umbonal slope in a subdued condition, and are not anywhere, 
abruptly terminated by the umbonal ridge as in characteristic specimens of G. 
alveata. In form and other characters these specimens do not differ from that 
species. 
This form is more abundant than any other in the Hamilton group, and is 
perhaps subject to greater variation from compression than any other of the, 
genus. When occurring in what appears to be its normal condition, the shell 
is much longer on the posterior end ; but many of the individuals in the collec¬ 
tion have been so distorted as to leave this part of the shell not more than half 
as long as the anterior end. The same degree of distortion is liable to occur in 
the height or depth of the valves, so as to produce an almost endless variety 
of form. 
This species occurs in all the localities cited for G. alveata. 
