43© 
PALAEONTOLOGY OF NEW-YORK. 
Estonia peculiaiis. 
Plate CL Fig. 2 a- g; and Plate Cl A. Fig. 1 a - h. 
For description of the species, see page 244 of this volume. 
PLATE Cl. 
Fig. 2 a, b, c. Dorsal, ventral and profile views of a specimen, having the ordinary form 
and proportions of this species in the Oriskany sandstone. 
Fig. 2 rf. A cast of the dorsal valve of this species, showing the median septum and lateral 
lamellse. 
A cast of the ventral valve, showing the form of the muscular impression, the 
median septum, and the small points of attachment for the adductor muscles. 
A specimen preserving a portion of the shell, which, on one side, is penetrated by 
the ramifying vessels. ( The lamellose structure of the shell is confounded with 
the surface striae in the figure, which gives it an unnatural appearance.) Figure 
enlarged to one and a half diameters. 
A cast of the ventral valve, showing the muscular and vascular impressions ( See 
corrected figure on Plate Cl a). 
PLATE Cl A. 
Fig. 1 a. Interior of the ventral valve, showing the form of the muscular impressions, teeth, 
etc. 
Profile of the same, showing the little elevations of the shell-surface, and the small 
pits for the adductor muscles a, and the teeth t. 
The dorsal valve, showing the crural processes and muscular impression. 
Front view of the same, showing the deep sinus, and the relation of the crural 
processes and median septum. 
Section of the dorsal valve, showing the elevation of the median septum and the 
crural processes. 
Figure of the ventral valve (the inflected extension in front being removed ) with 
a part of the dorsal valve attached, showing the crural processes c 1 and c 2, 
and the median septum of the dorsal valve ; a , the adductor imprints, showing 
the small oblique pits penetrating beneath the laminae of the shell ; r, the cardi¬ 
nal muscular impression. 
View of another specimen with the dorsal valve downwards and the ventral valve 
broken away, to show the median septum articulating with the bifurcating cardi¬ 
nal process of the dorsal valve. 
A cast of the ventral valve, showing the muscular and vascular impressions. This 
and the preceding figure are enlarged to once and a half the natural size. 
Geological 'position and localities. In the Oriskany sandstone : Albany, Schoharie, 
and Greene counties (New-York); Cumberland (Maryland ), and other places. 
Fig. 1 b. 
Fig. 1 c. 
Fig. 1 d. 
Fig. 1 e. 
Fig-1/- 
Fig- 1 g- 
Fig. 1 h. 
Fig. 2 c. 
Fig-2/. 
Fig. 2 g. 
