PLATE VII. 



(Figures 1-24, -29-32 by R. P. Wuitfield; 33-85 by F. B. Meek; 25-28 copies.) 



Legem!. A.. Canlinal area. 



DA. Oaiiiiiii'l area, brachial valve. 

 VA. Cardinal area, pedicle-valve. 

 F. Foramen. 



D. Deliidium. pedicle-valve. 

 A. Dflthyiiuni, pedicle-valve. 

 C. Delti iium, brachial valve, 

 t Teeth. 



d. De.ual lamella;, 

 b. Dental sockets. 



j. Cardinal process, 



c. Criu'a. 



s. Septum. 



X. Umbonal vault, 



y. Cast of umljonal vault. 



p. Pedicle muscular scar, 



a. Anterior adductors, 



a'. Posterior adductors. 



r. Diductors. 



lilllPIDOMELLA, CEhlert. 



I'age 208. 

 (.See Plates VI, VIa.) 

 Ortuis Pecosi, Marcoii. 

 Vig. 1. An entire specimen viewed from the brachial valve. X 2. 

 Fig. 2. Profile of the same. X 2. 



Fig. 3. The interior of the pe<licle-valve ; showing the narrow cardinal area and the characteristic mus- 

 cular scars. X 2. 

 Fig. 4. An enlargement of the surface ; showing the openings of the oblique tubules and minute punctae. 

 Coal Measui-es. Near Springfield, Illiiuns. 



Fig. 10. 



Orthls Penniana, Uerl)y. 



View from the pedicle-valve. 



Pi-ofile of the same specimen. 



The interior of the pedicle-valve ; showing the nearly obsolete cardinal area and the strong mus- 

 cular impi'essions, especially that of the pedicle-scar. 



The interior of an imperfect brachial valve ,- showing the cardinal process, crui'al bases and mns- 

 culai" impressions. 



The cardinal portion of the same specimen, enlarged to show the low, thick ('ardinal process, the 

 vei'y prominent crura and the quadripartite chai'actei' of the adductoj' area. X 3. 



An enlai'gement of the external surface ; showing strong punctation. 

 Coal Measures. Itaituba, Brazil. 



OKTIIOTICHIA, NOM. propos. 



Page -213. 

 OrTHIS (?) MORGANIANA, Dorbv. 



Figs. 11, 12. Interiors of iraiierfect brachial valves ; showing the cardinal process, the greatly elevated and 

 curved crura supported by septal plates which are produced about the sides of the mu.scular 

 area. In tig. 12 ai'e also seen the accessory adductor scars described by Dr. Derby. 



Fig. 13. Section in pi'otile of tig. 12 ; showing the extent of the crural plates and the elevation of the crura. 



Fig. 14. The interior of a pedicle-valve, retaining the long dental lamellEe and the median septum. 



Fig. 15. A slightly oblique view of another interior of this valve ; showing more distinctly the elevation of 

 the teeth and the' outline of the muscular area. 

 Coal Measures. Itaituba, Brazil. 



Genus BILLINGSELLA, ren. xov. 



P.ige 230. 

 (See Plate VIU, figs. 7-9.) 



BiLLINGSELLA PePINA, Hall. 



Fig. 16. The exterior of a brachial valve ; drawn from a gutta-percha impression of a natural mould. 

 Fig. 17. A natural cast of the interior of the brachial valve. 



Fig. 18. The extei'ior of the pedicle-valve. . 



Fig. 19. A natural cast of a pedicle-valve ; showing the high cardinal .area, the convex delfidium, the fill- 

 ing of the rostral cavity and the vascular sinuses in the pallial region. 

 Potsdam sandstone. Lake Pepin, Wisconsin. 



