PLATE 21. 



Fig. 1. ]46. 9. Lept^na sertcea. ( Pag. 59.) 



1 a. A large individual, 'preserving the shell uearly entire. 



1 b. A specimen presei-ving 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 same, showing the strong pnncta 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. Lept-t.na cop.rugata. (Puq-. 59.) 



2 a. A young individual, with the stria> very une(pial, and the folds on tljc hinge-line scarcely conspicuous. 

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



2 c. The interior of a dorsal valve, showing the striie eqiurlly bifurcating. 



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



portions; the concentric strife being still partially preserved. 

 2 c. An obscure cast in sandstone, where the strife appear to be nearly equal. 



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



Fig. 3. 444. 19. Lept^ena patenta. ( Pag. 60.) 



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

 S 6. The exterior of the concave valve of another individual. 



8 f. A portion of the surface enlarged. 



Fig. 4. 445. 20. Lept^ena profunda. (Pag. 61.) 



4 a. The interior of the ventral valve, whieh is worn on tiie upper part, and striato-punctate below. 



4 6. A portion of the surface enlarged. 



Fig. 5. 445. 20. Lept^na profunda? {young shelll). (Pag. 61.) 



5 a. Outer surface of .specimen. 5 h. Profile view of the same. 5 c. The strips enlarged. 



Fig. 6. 446. 21. Leptjena obscura. (Pag. 62.) 



G a. Specimen found in Sa(|uoit creek. 

 G b. Cast from the shaly sandstone associated v.itli the ore beds in the town of Kirkland. 



Fig. 7. 447. 22. Lept^na orthididea. ( Pag. 62.) 



7. Cast of the dorsal valve of this s[iecies, from a fragment containing several others. 



Fig. 8. 448. 23. LEPpiENA depkessa. (Pag. 62.) 



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



9 a. Tlie specimen, natural size. 9 b. The crenulated hiiige-line, enlarged. 



Fig. 10. 450. 1. Chonetes cornhta. (P''^2- ^^■) 



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 c, /. Enlarged portions of casts of the hinge and dental processes of the dorsal and ventral valves, as seen 

 under a magnifier. 10 sr. Portion of the surface enlarged. 



