PLATE -21. 



Fig. 1. 146. 9. LeptvKna sri<^ea. ( Pag. 59.) 



1 a. A large iiulividual, presciviiig ihe shell nearly eulire. 



1 6. A siiei-iiiK-ii preserving a portion of the shell, and showing in the cast the puncta which arc so charac- 

 teristic in this species. 

 1 c. A cast of the s;inie, 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 c. A similar portion of the cast, showing the puncta. 



Fig. 2. 443. 18. Lei'txna corrugata. ( Pag. 59.) 



i a. A young individual, with the strite very unequal, and the folds on the hinge-Iinc scarcely conspicuous. 



2 b. A larger individual, with the shell partially removed from near the beak. 

 2 c. The interior of a dorsal %Tilve, showing the stria; equally bifurcating. 



'2d. An old individual, with the shell entirely removed about the beak, and partially removed from other 



portions; the concentric stria? being still partially preserved. 

 2 e. An obscure cast in sandstone, where the strise appear to be nearly equal. 



2 /. A portion of the surface of the shell enlarged. 



Fig. 3. 444. 19. Leptjena patekta. (Pag. 60.) 



3 a. The interior of the concave valve, showing the muscular impression. 

 3 4. The exterior of Uie concave valve of another individual. 



3 c. A portion of the surface enlarged. 



Fig. 4. 445. 20. Lept.ena profunda. (Pan-. 61.) 



4 a. The interior of the ventral valve, whicli is worn on the upper part, and striato-pundate below. 



4 6. A portion of the surface enlarged. 



Fig. 5. 445. 20. Lept.sna profunda? (ijoinig shell?). (Pag. 61.) 



5 o. Outer surface of specimen. 5 i. Profile view of the same. o c. The stria; enlarged. 



Fig. 6. 446. 21. Lept^na obscura. (Pag. 62.) 



6 a. Specimen found in Saquoit creek. 



6 4. Cast from the shaly sandstone associated with the ore beds in the town of Kirkland. 



Fig. 7. 447. 22. Leptjjna oktiiididica. ( Pag. 62.) 



7. Cast of the dorsal valve of this species, from a fragment containing several others. 



Fig. 8. 448. 23. Leptj-xa dei>rfssa. ( Pag. 62.) 



Fig. 9. 449. 1. Stkophooonta prisca. (Pag. 63.) 



9 a. The specimen, natural size. 9 4. The crcnulated hinge-line, enlarged. 



Fig. 10. 450. 1. Chonetes coiiNcTA. (F^g- 64.) 



10 a, 4. Two specimens of the natural size (ventral and dorsal views), having the spinifnrm 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 c, 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. 



