I 



PLATE 59. 



Pago 



Figs. 1-11. Amphioenia elongata 383- 



1. Dorsal valvo of a specimen of racdivim size. 



2. Dorsal view of another individual of a more regularly elliptical form, showing a strongly 



striated surface. 



3. Ventral side of a much elongated spacimen preserving the shell on the upper part. 

 4-G. Protile. dorsal and cardinal views of a specimen of medium size and form. 



7. Interior of an imperfect dorsal valve, showing the hinge-plate, dental sockets, vascular lines, etc. 



c c, points for the attachment of the crura; /, foramen which passes beneath the hinge 

 plate and opens between the septa; t s. the double septum bordering the adductor mus- 

 cular scar. 



8. Dorsal view of a partial cast, showing muscular impressions and vascular lines, the cavity 



left by the removal of the hinge plate and at /, the filling of the foramen which passes 

 from the beak beneath the hinge plate. 

 9 Cast of a large dorsal valve, showing the muscular impressions and the cavity left by the 

 removal of the hinge plate, the filling of the foramen, etc. 



10. Longitudinal section of a specimen, showing the septa and processes of both valves: a, the 



thickened shell of the dorsal valve; c, the crura with its expansion to form the loop; ds, 

 dorsal septum; s. ventral septum; x, one of the dental lamellae which unite on the sep- 

 tum to form tlie spoon-shaped process of the ventral valvo. 



11. Cardinal view of a large cast of both valves; /, the filling of the for.imen of the dorsal 



valve, showing itj connection with the interior ; s, the cavity left by the removal of the 

 septum; x, the filling of the inside of the spoon-shaped process. 



