PLATE 21. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
I- 146. 9. Leptjena sericea. ( p a g. 59.) 
1 a. A large individual, preserving the shell nearly entire. 
I b. A specimen preserving a portion of the shell, and shewing in the cast the puncta which are so charac¬ 
teristic in this species. 
1 c. A cast of the same, showing the strong puncta produced hy the small spines of the interior of the shell. 
1 d . A portion of the shell enlarged, showing the larger and smaller stria. 
1 e. A similar portion of the cast, showing the puncta. 
2. 443. 18. Lept^ena corrugata. (p a g. 59.) 
2 a. A young individual, with the striae very unequal, and the folds on the hinge-line scarcely conspicuous. 
2 b. A larger individual, with the shell partially removed from near the beak. 
2 c. The interior of a dorsal valve, showing the striae equally bifurcating. 
2 d . An old individual, with the shell entirely removed about the beak, and partially removed from other 
portions; the concentric striae being still partially preserved. 
2 e. An obscure cast in sandstone, where the striae appear to he nearly equal. 
2 /. A portion of the surface of the shell enlarged. 
3. 444. 19. Leptjena patenta. ( P a g. 60.) 
3 a. The interior of the concave valve, showing the muscular impression. 
3 b. The exterior of the concave valve of another individual. 
3 c. A portion of the surface enlarged. 
4. 
445. 20. 
Leptasna profunda. 
(Pag. 
61.) 
4 
a. The interior of the ventral valve, which is worn on the upper part, and striato-punctate below. 
4 
b. A portion of the surface enlarged. 
5. 
445. 20. 
Leptjena profunda? (young shell ?). 
(Pag- 
61.) 
5 
a. Outer surface of specimen. 
5 b. Profile view of the same. 5 c. The striae enlarged. 
6. 
446. 21. 
LePT-ENA OBSCURA. 
(Pag- 
62.) 
6 
a. Specimen found in Saquoit creek. 
6 
b. Cast from the shaly sandstone associated with the ore beds in the town of Kirkland. 
7. 
447. 22. 
LePTjENA orthididea. 
(Pag- 
62.) 
7. 
Cast of the dorsal valve of this species, from a fragment containing several others. 
8. 
448. 23. 
Leptaena depressa. 
(Pag- 
62.) 
9. 
449. 1. 
Strophodonta prisca. 
(Pag. 
63.) 
9 
a. The specimen, natural size. 
9 6. The crenulated hinge-line, enlarged. 
Fig. 10. 450. 1. Chonetes cornuta. (Pag. 64.) 
10 a, b. Two specimens of the natural size (ventral and dorsal views), having the spiniform tubes attached. 
10 c. A small fragment of green slate, with several valves upon the surface, some of them destitute of spines. 
10 d . The dorsal valve enlarged, showing its appearance when magnified to double the natural size. 
10 e, f. Enlarged portions of casts of the hinge and dental processes of the dorsal and ventral valves, as seen 
under a magnifier. 10 g. Portion of the surface enlarged. 
