PLATE VII. 



(Figures 1-24, 29-32 by R. P. WuiTFIULD; 33-35 by P. B. Mbbk; 25-28 copies.) 



Legend. A. Cardinal area. 



DA. Cardinid area, brachial valve. 

 VA. Cardinal araa, pedicle-valve. 

 F. Foramen. 



D. Uellidium. pedicle-valve. 

 ^. Oelthyrium, pedicle-valve. 

 C. Delti iium, brachial valve. 

 t Teeth. 



d. Deiital lamellse. 

 b. Dental sockets. 



j. Cardinal process, 

 c. Ci'ura. 

 s. Septum. 

 X. Umlional va\ilt. 

 y. Cast of umbonal vault, 

 p. Pedicle mu.scular scar, 

 a. Anterior adiluctors. 

 a'. Postei'ior adductors, 

 r. Diductors. 



KHIPIDOMELLA, CEhlert. 



Page 208. 

 (See Plates VI, VIA.) 



Orthis Pecosi, Maicoii. 



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

 Fig. 2. Pi-ofile of the same. X 2. 



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

 cular scars. X 2. 

 Fig. 4. An enlai-gement of the surface ; showing the oiienings of the oblique tubules and minute punctse. 

 Coal Measures. Near Springfield, Illinois. 



Fig. 10, 



Orthis Penniana, Derby. 



View from the pedicle-valve. 



Pi-ofile of the same specimen. 

  The interior of the peilicle-valve ; showing the nearly obsolete cardinal area and the sti'ong mus- 

 cular impressions, esjiecially that of the pedicle-scar. 



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

 culai' impre.ssions. 



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

 vei'y prOMiinent ci'ura and the quadi'ipartite character of the adductor area. X 3. 



An enlargement of the external surface ; showing strong punctatiou. 

 Coal Measures. Itaituba, Brazil. 



ORTHOTICHIA, xom. propos. 



Page 213. 

 OUTHIS (?) MORGANIANA, Deibj. 



Figs. 11, 12. Interiors of imperfect brachial valves ; showing tlie cardinal pi-ocess, the greatly elevated and 

 curved crui'a suppoi-ted by septal plates which are produced about the sides of the muscular 

 area. In tig. 12 are also seen the accessory adductor scars described by Dr. Dekby. 



Fig. 13. Section in profile of fig. 12 ; showing the exteiit of the crural plates and the elevation of the crura. 



Fig. 14. The inteiior of a pedicle-valve, retaining the long dental lamellae 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, gen. nov. 



Page 230. 

 (See Plate VIIa. figs. 7-9.) 



Billinosella 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 intei'ior of the brachial valve. 

 Fig. 18. The exterior of the pedicle-valve. 



Fig. 19. A natural cast of a pedicle-valve ; showing the high cai'dinal area, the convex deltidium, the fill- 

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

 Potsdam sandstone. Lake Pepin, Wisconsin. 



