PIATE 52. 

 Fig. 1. 612. 25. Ohtiiis pisuM. ( Pag. 250.) 



1(7, b. Young spcrinu'iis of this spock's. 



1 c. The voutriil valve of a full grown indiviilual, showing tlu' beak of the dmsal valve. 



1 (I. I'rolile view of the same, the shell slightly compressed. 1 e. View of the beaks of the .same. 



Fig. 2. 613. 26. Orthis pykamidalis. (Pag. 251.) 



2 a, b, c, d. Dorsal, ventral, cardinal and prolile views of a specimen of the ordinary size. 

 2 e, /, g, li. Similar views of a much larger shell. 



2 i. An enlargement of the surface, showing the sharp plications crossed by concentric stria;. 



Fig. 3. 440. 22. Orthis elegantula. (Pag. 252.) 



3 a, b. The dorsal valves of young individuals. 



3 c. The dorsal valve of a full grown individual, having the beak somewhat more extended than in other 



specimens. 

 8 d. Ventral view of the same specimen. 3 e. Profile view of the same si)ecimen. 



3 /. Cardinal view of the same, showing the elevation of the dorsal valve. 

 3 g. Ventral view of a shorter specimen. 3 h. Cardinal view of the same. 



8 i. Cast of a dorsal valve of an elongated specimen. 3 k. Cardinal view of the same. 



3 /, m. The interior of the dorsal valves of a young and full grown individual. 

 3 71. The interior of a ventral valve, showing tlu^ muscular iniprcsssion, lamella", etc. 

 3 0. The same enlarged. S p. The interior of a similar sliell, showing a slight variation in character. 



3 r. Cardinal view of the same, showing the dental lamelhe, and the callosity at the apex of the foramen. 



3 s. An enlargement of the surface. 



Fig. 4. 614. 27. Orthis HYBTiiDA. (Pag. 253.) 



4 a, b, c. Figures of specimens showing three gradations of size. 

 4 d, e. Cardinal and profile views of fig. 4 c. 



4 /. A specimen having the valves more convex than usual. 



4 g. Profile view of the same specimen, showing the nearly equal convexity of the valves. 



4 A. A cardinal view of a specimen, showing the convexity of the dorsal valve. 



4 i, k. The interior of the dorsal valve of this species, .showing the muscular impression divided by a longi- 

 tudinal ridge. 



4 /. An enlargement of the muscular impression of the preceding specimen. 



4 m. The interior of the ventral valve, with a scarcely defined muscular impression. 



4 7i. A cast of the ventral valve of this species, showing the bilobate character of the muscular impression, 

 the cavities of the teeth, etc. 



4 o. \u enlargement of the surface, showing the longitudinal diverging and fine concentric strias. 



Fig. 5. 615. 28. Oethis puncto-striata. ( Pag. 254.) 



5 a. View of the ventral valve of a small specimen, showing the beak of the dorsal valve, and a part of the 



area .above it. 5 6. A profile view of the .same specimen. 



6 c. A cardinal view of a Larger specimen, showing the great convexity of the valves. 



5 d. A large dorsal valve which has been flattened by pressure. 5 e. The interior of the same. 



5 /. Several of the striaj enlarged, showing the puneta between. 



Fiff. 6. 616. 29. Ortiiis flabellulum, Var.? ( Pag. 254.) 



Co, b, c. Dorsal, profile and ventral views of a compressed specimen. 



6 d. The interior of a ventral valve. G c. A cast of a ventral valve. 

 6 /. Cardinal view of a specimen, which is partially a cast. 



6 g. Cardinal view of the specimen fig. 6 o. 



Fig. 7. 616. 29. Orthis FLABELLULUM? Var.? ( Pag. 255.) 



7 a, b. Dorsal and ventral views of the specimen. 



7 c. Profile view of the same. ' 7 d. Cardinal view the same. 



Fig. 8. 617. 30. OuTHis FASciATA. ( Pag. 255.) 



8 o. A cast of the ventral valve, showing an extended hingc-linc. 8 b. A cast of the dorsal valve. 



