LAMELLIBRANCHIA TA. 
363 
many individuals, it may be suggested that these are only old shells in which 
the conspicuous markings have become obsolete. An approach to this condi¬ 
tion is seen in fig. 8 of plate lvii, which is referred to G. nodocostata. 
Formations and localities. In the arenaceous shales of the Hamilton group, in 
Schoharie, Otsego, Chenango, Madison and Onondaga counties, and in the Che¬ 
mung group at Ithaca, N. Y. 
Grammysia erecta. 
PLATE LVI, FIG. 8 ; and PLATE LVII, FIG. 10. 
Grammysia erecta, Hall. Prelim. Notice Lamellibranchiata, 2, p. 52. 1870. 
“ magna. Hall, in error. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 56, fig. 8; pi. 
57, fig. 10. 1883. 
Shell of medium or large size, erect, sub-triangular; length one-fourth greater 
than the height; basal margin gently rounded except where slightly sinuated 
by the cincture near the middle of its length; posterior margin abruptly 
rounded below and recurving to the cardinal line, Avhich is short. Anterior 
end below the lunule, broadly rounded. 
Yalves regularly convex below and gibbous above. 
Beaks sub-anterior, very prominent and strongly incurved. Umbo ven- 
tricose; umbonal slope rounded and arcuate. Cincture in the right valve, 
consisting of a fold and shallow furrow on each side, beginning at the beak, 
and extending in a curving direction to near the middle of the base. 
Surface marked by fine concentric striae, which become fasciculate on the 
anterior half of the shell, and form strong angular elevations. These con¬ 
centric undulations extend over the entire umbonal region, and are abruptly 
sinuate in passing the cincture. Surface also marked by extremely fine 
radiating striae. 
This species differs from any of those having a cincture, in its erect form and 
sub-triangular outline. The specimens are distorted and fragmentary, and 
therefore unsatisfactory. 
Formation and locality. In the shales of the Hamilton group, at Fultonham, 
Schoharie county, N. Y. 
