PLATE LXXVIII. 



(Flgtirw •-«. "-■'S* '>> ^' B^iM''s<»: in-lf.by K. P. \Vhitfiei.d.) 



Genus NEWBEKKIA, Hall. 



ratre 261. 



Newbekria Clayiolii, Hall. 

 K«f. I. An internal cast of a ^lortion of the pe<lii-le-valve ; showing the divergent impi-essions of the dental 



lamellc ; the iri-egiilaily divide<i seal- of the adductor muscles ; the narrow anterior adductor 



and strong vascular inijiivssions. 

 Fig. 2. A portion of the interior of the brachial valve, di-awn from a gutta-percha impreeeion of a natural 



internal cast ; showing the dixisimi of the hinge-plate, and the st' iated adductor impressions. 

 Pig. 3. An internal cast of a small pedicle-vai\i; in wliich the impressions of the vascular sinuses are very 



strongly developeti. 

 Fig. 4. An internal cast of a bi-achial valve preserving the usually elongate form of mature individuals, 



and showing the mus<'ular and va.«riilai- impi-essions. 

 Fig. 5. The interior of a pe<licle-valve, fi-om a gutta-percha impi-ession ; showing an open delthyrium, the 



divergent ilenlal | lates, the musitular and vascular impres-sions. 

 Fig. 6. An internal cast of the pedicle-valve ; showing the impi'ession of the apical cup-shaped depression 



of that valve. By the removal of the tilling of the dental sockets, the cardinal slope is made to 



appear unusually lai-ge and flat. 

 Fig. 7. An internal cast of a large and symmeti-ical pedicle- valve. 

 Fig. 8. An internal cast of a large and somewhat defoi-med brachial valve, which shows the usual size 



and division of the hinge-i)late and the character of the adductor scars. 

 Kg. 9. An internal cast of a pcilicle-va'.ve in which the muscular scars and vascular sinuses, both pri- 

 mary and secondary, are highly developed. 



Sandstones of the Hamilton group. Perry county, Pennsylvania. 



Newbekria Johannis, Hall. 



Fig. 10. An internal cast of the umbonal portion of a pedicle-valve, with the muscular and va.<icular mark- 

 ings distinctly retained. 



Rg. 11. An inteiTial cast of the upijer portion of a brachial valve ; showing the cavity left by the divided 

 hinge-j)late and the adductor nuiscular scai-s. 



Pigs. 12, 13. Dorsal and ventral views of a lai-ge and characteristic specimen ; showing the elongate-oval 

 form, the <lecided medi.in .ingulation of the valves and the rugose concentric growth of the 

 surface. 



Pig. 14. The exterior of a i>edicle-valve of a small individual. 



Pigs. 15, 16. Dorsal and protile views of a similar specimen ; showing the convexity of the valVes. 

 Hamilton gi-oup. WaterUm, lotca. 



Newberria Litvis (Meek Jsp.), Whiteaves. 

 Figs. 17, 18. Dorsal and ventral views of an internal (!ast of a very large an<i symmetrical individual ; 

 showing the striate<l anterior a<l(Iuctoi- scars on the brachial valve, and the elongate muscular 

 area, with the casts of the va.s<-ulHr sinuses in the lunbonul region of the pedicle-valve. The 

 line railiating stria,- near the anterior margin of the specimen belong to the inner lamin.Te of the 

 shell. 

 FigB. 19, 20. Profile and dorsal views of an individual retaining the shell, and showing the normal convex- 

 ity of the valves. 



Hamilton group, Jiarapartu of the Mackemie River, Britlih Avurrica. 



Newbekria Missouriensis, Swallow. 



VigB. 21, 22. Ventral and ilorsal views of an indiviilual fnmi which the shell is partially exfoliated, exjuMug 



the muwMdar an<i vasf.'ular inijires.'iions on the pedicle-valve. 

 Fig. 23. Protile of a large, gibbous individual. 



Hamilton group. MuniUav, county, Missouri. 



