PLATE 49. 



Pag« 



Fig. 1. Tellinomya nucleiformis. 263 



1. A cast of the left valve. 



Fig. 2 a - e. Modiolopsis? dubius. 264 



2 a. The right valve of a specimen which is slightly imperfect at the posterior extremity. 



2 6. Cardinal view of the same. The apparent gaping at the posterior extremity is due to 

 imperfection of the specimen. 



2 c. The right valve of this species. 



2 d. Tlie left valve of a larger individual. 



2 «. A fragment of limestone preserving the separated valves of several individuals. 



Fig. 8 a - d. Anatina? sinuata. 265 



3 a. The right valve? of a specimen in which the two extremities are imperfect. 



3 6. Cardinal view of the same. The compression of the anterior extremity is not distinctly 

 represented. 



3 c. The right valve? of a specimen from which the shell is nearly exfoliated, and the beaks 

 broken off. 



3 d. Profile view of the same 



Fig. 4. Megambonia suboebicularis. 278 



4 a. The left side of the cast, showing the muscular impression. 



5 6 ( by error for 4 4 on plate). Profile view from the posterior side. 



Fig. 5. Megambonia spinneri. 274 



5 a. The left side of the cast, showing the form, the muscular scar, and elevation of the beak. 



4 6 ( by error for 5 6). Profile view from the posterior side. 



5 c. Cardinal view, showing the prominence of the muscular scars. 



Fig. 6. AvictiLA obscura. 280 



6. Interior of a right valve, having the anterior wing nearly obliterated, and the other broken 

 off at some distance from the extremity. 



Fig. 7 & 8. Megambonia aviculoidea. 274 



7 a. The left valve of a young shell. 

 7 6. The left valve of a larger individual. 



8. A full-grown? individual preserving in part the anterior and posterior extensions, the shell 



being removed from the central prominent part of the fossil. 



Fig. 9. Megambonia ehomboidea. ^ 275 



9. The left valve, imperfect at the posterior side, and also at the anterior side, though the 



latter is not shown in the figure. 



