PLATE XI. 



(Figures 1-23 by K. P. Whiti'Ield.: 



Leg-piiil. D. Deltiiliiiin, jiedii-le-valve. 

 C. Deltidiuiii, brachijil valve, 

 t. Teeth. 



d. Dental lamellse. 

 b. Dental socket.s. 

 ('. Crural plates. 



Mi'dian sejituni. 

 Cardinal pror.ess. 

 Diductor scars. 

 Anterior addiii-.tovs. 

 Postei-ior adduclors. 



Genus DKRBYA, Waagen. 

 Dkrbya Keokuk, Hull. 



Fig-s. I, 2. All internal cast and gutta-percha impression of the central cardinal area, viewed from the bra- 

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

 lamellse and median septum. 



Keokuli beds (Knobstone group). A^ew Providence, Indiana. 

 Fig. 3. An parti.al cast of the interior of a pedicle-valve ; showing the muscular scars and impression of 

 the median septum. 



Keokuk beds. Keokuk. Imoa. 



DeRBYA (?) RILOBA, Hail.* 



Fig. 4. A cardinal view ; showing the ventrico.se brachial valve and short area of the pedicle-valve. X 2. 

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

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

 Coal Measui'es. Winterset, Iowa. 



STREPTORHYNCHUS, King. 



Page 267. 



Stkeptorhynchus Hallianus, Dcrliy. 



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



Fig. 7. A posterior view of the cardinal process ; showing the lobation of the posterioi- face, the elevated 



crural plates and the grooved deltidium. X 2. 

 Fig. 8. An enlarged view of the same parts, fi'om above ; showing also the character of the aiUluctor im- 



pi-essions. X 2. 

 Fig. 9. The cardinal process of a larger individual ; 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 jirocess of another specimen ; showing a greatei- elevation and deeper bifurcation. 

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



mai-gin, ami showing the strongly alternating strise. 

 Fig. 14. The interior of the same valve ; showing the unsupported teeth, and the chai'acter of the muscu- 

 lar scars. 

 Fig. 1."). The exterior of a pedicle- valve, having a plicated extei'ior similar to that of Mebkklla and Strep- 



Un-hynchus pectiniformis, Davidson. The shell is unsymmetrical and the outline is partially 



restored. 

 Fig. 16. The interior of the same specimen ; showing the cardinal area, closed delthyrium, the pi'ojecting 



teeth, and the flabellate nuiscular impression. 

 Fig. 17. A view looking into the umbonal cavity of the specimen represented in fig. 14; showing the 



absence of dental lamellse and median septum. 



Upper Carboniferous. Bomjardim and Itaituba, Pro-mnee of Para, Brazil. 



• Report of the New York State Geologist for 1882 (pub. 1883), explanation of plate (xi) 11, figs. 4 and 5. 



