PLATE LXXVII. 



(Figures 1-9, 2S-2n by K. B. Meek ; 10, 11, 17-2i by G. B. Simpson ; 12-14 by R. P. Whitfield ; 26-28 by F. J. Swinton.) 



Subgenus BP^ACHIA, s.-gen. nov. 



Page 260. 



Beachia Suessana, Hall. 



Fig. 1. The interiore of two pedicle-valves, the upper retaining the deltiilial plates, the lower having 

 lost the?e ) lates, but showing the dental lamellae. Both tigures show an obscure muscular 

 area divided by a low median ridge. 



Fig. 2. The interior of a brachial Valve ; showing the hinge-plate, medially depressed and perforated at 

 its apex by the viscei'al foramen, the (iental sockets, and the form of the loop with the median 

 rod-like process extending backwaiil and upward from the anterior plate. 



Fig 3. Front view of conjoined valves ; showing the tine plication of the surface and the inflexion of the 

 lateral margins. 



Fig. 4. Median longitudinal section of conjoined valves; showing in profile the loop with its long, erect 

 crural apophyses, the elevation and direction of the median process extending backward from 

 the anterior plate. 



Fig. f). Views of the interior of two brachial valves ; showing the inflected lateral margins and some vari- 

 ation in the comlition of the hinge plate. 



Figs. 6, 7, 9 Ventral, profile and doreal views of a typical example ; showing the outline, contour and 

 plication of the valv(>s and their lateral marginal inflexion. 



Fig. 8. Profile of a smaller shcl!, with the marginal inflexion of the valves extending to the anterior ex- 

 tremity. 



Figs. 10, 11. Views of the hinge-plate in two individuals ; showing differences due to age and consequent 

 thickening of the parts. X 2. 



Oriskany sandstone. Owtiiherland, Maryland. 



Genus MEGALANTEKIS, Suess. 



Page '277. 



Megalanteris ovalis, Hall. 



Fig. 12. An internal cast of the pedicle-valve ; showing the filling of the deep scar of the diductor muscles, 



enclosing the small subcordate atlductor scar, with traces of vascular sinuses and genital 



markings. 

 Fig. 13. The doi-sal side of an internal cast ; showing the deep impression of the prominent hinge-plate 



and cardinal process, and the adductor muscular seal's. 

 Fig. 14. A similar view of another specimen to which a portion of the pedicle-valve adheres ; showing the 



cavity of the hinge-plate and the division of the muscular area into anterior and posterior 



scars. 



Oi-iakany sandstone, f^choharie, New Turk. 



Fig. 15. The ventral side of another internal cast ; showing the impressions of the muscular scars and vas- 

 cular sinuses. 



Fig. IB. Doi-sal view of the same specimen ; shiwing the deep cavities left by the grooved cardinal pro- 

 ce.SH, crural bases, and adductor scars. 



Figs. 17, 18. Posterior and interior views of the cardinal portion of the brachial valve, enlarged; showing 

 the hinge-plate and the stout, erect, biloVied and deeply grooved cardinal process, the broad 

 crural ba-ses, and a portion of the muscular impression. X 2. 



Figa. 19, 20, 21. Interior, profile and fnmt views of a gutta-percha impression taken from a natural cast of 

 the interior, having 9, very highly developed cardinal process divided on its posterior face by 

 a single median groove ; showing also the crural bases and muscular area divided by a low 

 median septum. 



Fig. 22. The umbonal portion of the brachial valve, drawn Jrom a gutta-percha impression taken from the 

 specimen repre.sented in fig. 16. The two grooves on the posterior face of the cardinal process 

 are charactei-ized by series of tine, diverging lines. 



Oriskany sandstone. Albany county. New York. 



