PLATE XI. 



(Figures l-2'.> by R. P. Whitiield.) 



Legend. D. Dellidiuin, pcilide-valve. s. Median septum. 



C. Deltidiuin, braehial valve. j. Cardinal jjroi-es.s. 



t. Teeth. r. Diductor sears, 



d. Dental lamellEe. a. Anterior adihi<-,tiirs. 



b. Dental sockets. a'. Postei-ior addiiclcirs. 



c. Crural plates. 



Ge.nus I)P:KBYA. W aace.n. 



I'afCc-iKI. 



Dkkbya Keokuk, Hall. 



Figs. 1, 2. An internal cast and g-iitta-percha inijn'ession of the central cardinal .irea. viewed (Voni the bra- 

 chial valve ; showing the character and extent of the muscular area, cardinal process, dental 

 lamellse and median septum. 



Keokuk beds (Knobstone group). Nem Providence. Indiana. 

 Fig. 3. An jiartial ca.«t of the interior of a pedicle-valve; showing the muscular scars and impression of 

 the median septum. 



Keokuk beds. Keokuk. Iowa. 



DeKBYA (?) BILOBA, Hall.* 



Fig. 4. A cardinal view; showing the ventricose brachial valve and short area of the jiedii-le-valve. X 2. 

 Fig. 5. A view of the brachial valve ; .^ihowing the bilobed contour of the shell, obdurate outline, the short 

 cardinal area and deltidium of the opposite valve. X 2. 

 Coal Measures. Winterset, Iowa. 



STREl'TORHYNCHUS. King. 



Page 267. 



Streptorhynchus Hallianus, Deihy. 



Fig. 6, A view fmm the brachial valve of an entire shell. 



Fig. 7. A posteiior view of the canliual process ; showing the lobatiou of the jiosterior face, the elevfited 



crui'al plates and the grooved deltidium. X 2. 

 Fig. 8. An enlai'ged view of the s.ame parts, from above ; showing also the character of the adiluctor im- 

 pressions. X 2. 

 Fig. 9. The cardinal proce.ss of a lai-ger indiviilual ; showing the gi-ooving of the extremities of the lobes. 

 Fig. 10. A profile of the same ; showing the backward extension of the process and the great elevation of 



the crural plates. X 2. 

 Fig. 11. A posterior view of the same. X 2. 



Fig. 12. The cardinal process of another specimen ; showing a greater elevation and deeper bifurcation. 

 Fig. 13. The exterior of an unsymmetrical pedicle-valve ; slightly restored about the left ante-lateral 



margin, ami showing the strongly alternating striae. 

 Fig. 14. The interior of the same valve ; showing the unsupported teeth, and the character of the uuiscu- 



lar scars. 

 Fig, la. The exterior of a pedicle valve, having a plicated exterior similar to that of Meekklla and Strep- 



torliynchtis peHiniformi.'!. X>a\\dsvu. The shell is unsymmetrical and the outline is partially 



restored. 

 Fig. 16. The interioi- of the same specimen ; showing the cardinal area, closed delthyrium, the projecting 



teeth, and the fiabellate nmscular impression. 

 Fig. 17. A view looking into the umbonal cavity of the specimen repi-esented in tig. 14 ; showing the 



absence of dental lamellfe and median septum. 



Upper Carboniferous. Bomjardim and Itaituha, Prwoince of Para. Brazil. 



Kepoit of the New York State Geologist for 1882 (pub. 1883), explanation of plate (xi) 41, flgs. 4 and 5. 



