188 
PALAEONTOLOGY OF NEW-YORK. 
Fig. 1 g. The punctate surface shown where the shell is exfoliated. 
Fig. 2- The dorsal valve of a well-preserved specimen. 
Fig. 2 c. Profile of striae, showing the elevations and flat surfaces between them. 
Fig. 3. A ventral valve, probably of this species. 
The specimen, Plate xviii, fig- 3 a , presents characters which are somewhat 
intermediate to this one and S. punctulifera; the surface, when partially ex¬ 
foliated, showing the punctate character represented in fig. 3 h of same plate. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg mountains; Schoharie, Hudson, Oatskill, etc. 
Stropliodonta pimctulifera. 
Plate XXI. Fig. 4; and Plate XXIII. Fig. 4-7. 
Strophomena pundulifera : Conrad, Ann. Report on the Palaeontology of New-York, 1838, p. 117. 
— — Yanuxem, Geol. Report Third District of New-York, 1843, pa. 122, fig. 
S'. englypha : Conrad, Ann. Report Palaeontology of New-York, 1841, p.36. 
Shell subsemicircular, about four-fifths as long as wide. Ventral valve 
concave : beak not projecting beyond the hinge. Dorsal valve concave 
near the umbo, very convex near the middle : beak not elevated above 
the cardinal margin ; sides somewhat contracted below the extremities 
of the hinge. Hinge line straight, nearly or quite equalling the greatest 
width of the shell, finely crenulated. Area narrow, linear, vertically 
striated. Foramen nearly closed, with a narrow prominent callosity 
along the centre. 
Surface marked by strong sharp striae, which increase by bifurcation and 
interstitial addition, becoming rapidly more numerous and finer towards 
the margins, and are distinctly punctate in the best preserved speci¬ 
mens. 
The Strophomena pundulifera is described by Mr. Conrad as “Shell with the 
“ upper valve deeply concave : radiating strife very numerous, prominent, angu- 
“ lated, each with a series of very regular small elevated punctse. Length two 
u inches. Locality, Helderberg mountains.” 
The specimen, fig. 4, Plate xxi, was regarded by Mr. Yanuxem as this species; 
and it appears to be identical with a strongly,striated one in the Pentamerus lime¬ 
stone, which I have placed under the same designation. The striee, even in those 
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scarcely exfoliated, are marked by one or two rows of elevated pustules, which are 
