PLATE XXXI. 



(flfarM 1-8. 6-10. 1*. 15, 18, U by R. P. WuiTriBU); 4, 9, 11, IS, U, 16, 17 by F. B. Meek.) 



Legemi : A. Cardinal area. j. Cai'dinal process. 



Adt. Denticulated canlinal mai-gin. b. Dental sockets. 



D(f. Dellidial (fr<)Ove8. a. Adductor scars. 



s'. Callosity in delthyrium. r. Diductor scars, 

 t. Teeth. 



Genus SFIHIFER, Soweuby. 



rago I. 

 SpIRIFEB INCHEBESCENS, Hall. 

 See Plate SO. 

 Pigf. 1. A portion of the interior of the ]>edicle-ralve ; showing the denticulations along the cardinal mar- 

 gin, the delthyinal callosity and the form of the muscular scar. 

 Fig. 2. Corresponding portion of a brachial valve ; showing cardinal process and dental sockets. 

 Fig. 3. An enlargement of the cardinal area to show the denticulated cai-dinal edge of the pedicle-valve. 

 The surface of the shell on the area is somewhat exfoliated, exposing the sories of vertical 

 canals, each of which terminates in a denticle. The margin of the brachial valve shows a series 

 of small sockets corresponding to the denticles. 

 Chester limestone. Chester, lUinoit. 



Spibifeb ofihus, Hull. 



Figs. 4, 5. Brachial and profile views of a normal individual. 



Coal Measures. Iowa. 

 Pig. 6. The interior of the pedicle-valve ; showing the character of the muscular impression. 

 Fig. 7. The interior of a brachial valve. 



Coal Measures. Bornjardxm, Brazil. 



Spirifer Grimesi, Hall. 

 Fig. 8. A cardinal view ; showing the high, relatively short area, and the convexity of the valves. 

 Fig. 16. Doi-sal view of a nearly entire individual of normal mature size. 



Fig. 17. The interior of a portion of the pedicle-valve ; showing the structure of the muscular area. 

 Fig. 18. A portion of an internal cast of the pedicle-valve ; showing the impressions of the adductor and 



diductor muscular scai-s. 

 Fig. 19. Enlargement of the radiating surface stiite. 



Burlington limestone. Burlington, Iowa. 



Spirifer Newberryi, sp. nov. 



Rg. 9. The exterior of the brachial valve ; showing the fine plications. 

 Kg. 10. An enlargement of the surface ; showing the fine strite. 

 Waverly group. Ohio, 



Spirifer imbrex, Hall. 



Fig. 11. The exterior of a brachial valve. 



Fig. 12. An enlargement of the surface ; showing the bifurcating plications and the lamellose concentric strite. 

 Burlington limestone. Burlington, Iowa. 



Spirifer sub^qualis, Hall. 



Figs. 18, 14. Cardinal and dorsal views of the original specimen ; showing the imbricated exterior. 

 Warsaw limestone. Warsaw, Illinois. 



Spirifer Marionen.sis, Shuniiud. 



Fig. 15. A view of a rather small example ; showing the fasciculate plications. 

 Choteau limestone. Pike county, Missouri. 



