88 
PALAEONTOLOGY OF NEW-YORK. 
often rising in ridges which in the exfoliated shell do not show the divi¬ 
sions. Some specimens have the striae sharp and slender, and nearly 
equal, with wider plain intermediate spaces. On the dorsal valve the 
striae are pretty uniform; the stronger ones being distant, sharp and 
elevated, with wide intermediate spaces marked by extremely fine regular 
striae, from the midst of which, as the shell increases, the elevated striae 
arise, dividing the space in which the smaller striae are constantly in¬ 
creasing by intercalation. 
The modifications in the expression of the surface striae, in the specimens, are represented 
bii Plate xi, figures 25, 29, BO & 31, and on Plate xm, figures 6-8. In the lattter 
figures the striae are uneven, and rise in ridges with irregular interspaces. 
In figure 29, Plate XI, which is a cast of the ventral valve, there are regular interspaces 
between the fine elevated striae, a character more usually observed ir^the dorsal valve. 
The muscular impressions of the ventral valve show narrow elongate scars for the occlusor 
muscles, and the divaricator muscular impressions are spreading, flabelliform, and deep¬ 
ly striated. In many of the casts, the lower part of the specimen is marked By strong 
vascular impressions, which are shown in figures %6 & 27 of Plate xi. The muscular 
impressions of the dorsal valve are narrow and elongate, and the cardinal process is 
usually comparatively slender. The interior surface of the valves is granulose or pu- 
stulose. 
This species approaches the S. pp,tersoni; and in some specimens, it is not easy 
to decide the specific differences. In the latter species, the muscular impressions 
of the ventral valve are smaller and shorter, while the wide interspaces between 
the stronger striae on the ventral valve are characters not observed in any of the 
numerous authentic specimens of S. inequiradiata : at the same time, there are 
many obscure specimens in the Schoharie grit and Corniferous limestone, which 
it is difficult to refer satisfactorily to either of the species described. 
The S. inequiradiata is entirely distinct from the S. inequistriata of Conrad, with 
which it has been sometimes united*, as will be shown under the description of 
that species in the Hamilton group. 
Geological formation and locality. In the Schoharie grit in Albany and Scho¬ 
harie counties; and in the Corniferous limestone of the Helderberg mountains, 
Schoharie, Cherry-valley, and other places. 
It is perhaps unfortunate that the nanie has the same signification. 
