62 
PALAEONTOLOGY OF NEW-YORK. 
446. 21. LEPTiENA OBSCURA. 
Pl. XXI. Figs. 6 a, 6 b. 
Shell semioval, width and height in proportion of five to four ; hinge-line extending slightly 
beyond the width of the shell; dorsal valve nearly flat; surface marked by fine sharp striae, 
which bifurcate near the beak, and towards the margin increase by other smaller ones coming 
in between ; concentric markings not visible in our specimens. 
This species is nearly flat, and somewhat resembles L. corrugata ; but is destitute of the 
folds along the hinge margin, and the striae are likewise sharper. 
The specimen fig. 6 h is a cast in shaly sandstone; and the striae, though preserved, are less 
sharp, and apparently more numerous than in the shell 6 a : still there appears no specific 
difference between them. 
Position and locality. The specimen 6 a was found on the Saquoit creek south of Utica, in 
the position near the upper ore bed. The specimen 6 b is a cast from the shaly sandstone as¬ 
sociated with the ore beds in the town of Kirkland, Oneida county. ( state Collection.) 
447. 22. LEPTiENA ORTHIDIDEA. 
Pl. XXI. Fig. 7. 
Shell semioval, somewhat wider than high ; hinge-line rather less than the width of the shell 
below; dorsal valve slightly convex, finely striated ; striae somewhat in fascicles ; dental 
lamina thick at the foramen, and extending downwards into the shell with a gentle curve ; 
muscular space oval, scarcely wider below than above. 
The specimens which I have of this species, are all casts in shaly sandstone; but the cha¬ 
racters preserved are sufficient to distinguish it from any of the preceding. It has a peculiar 
Orthis-like aspect; and the striae being apparently sometimes in fascicles, contributes to this 
impression. The peculiar curving of the dental lamella is the distinguishing feature of the cast. 
Fig. 7. Cast of the dorsal valve of this species, from a fragment containing several others. 
Position and locality. In the shaly iron-stained sandstone associated with the ore beds in 
Kirkland, Oneida county. 
448. 23. LEPTiENA DEPRESSA. 
Pl. XXI. Fig. 8. 
This species is of somewhat frequent occurrence in this group, though it is usually some¬ 
what imperfectly developed, being often of small size and obscurely marked. I have given 
this cast of the dorsal valve, as indicating its occurrence simply at this period. 
This species, which may be identical with L. tenuistriata of the lower silurian strata, is 
not abundant in the Clinton group, but becomes abundant and well defined in the Niagara 
