PLATE XXXIII. 



(Figares 1-23, 27 by R. P. Whitfield; 2t-2(i bj- F. B. Meek.) 



Legend : A. Cardinal area. f. Fissure at base of dental sockets 

 D. Deltidium. (brachial valve), 



f. Foiaraen. g. Ro.stral callosity, 



t. Teeth. b. Dental sockets, 



s. Median septum. c. Crura, 



s'. Delthyrial callosity. sji. Sjiii-als. 



Dg. Margins of delthyrium (brachial a. Adductor scars, 



valve). r. Diductor scars. 



Genus SPIRIFER, Sowerby. 

 Spiruer tkibulis, Hull. 



The exterior of a brachial valve of an average example ; showing the lamellose surface. 

 The exterior of a brachial valve. 



The interior c.f a jiedicle-valve ; showing the character of the muscular area. 

 A. cardinal view of conjoined valves ; showing the elevation of the area. 

 Oriskany sandstone. Cumberland, Maryland. 



Spiuifer submucronatus, Hall. 



Fig. .5. The exterior of a normal example, retaining the deltidial covering and showing the foramen 

 Fig. 8. An enlargement of the cai'dinal portion of the same specimen ; showing the foramen at its 



summit. 

 Fig. 7. An enlargement of the surface ; showing fine radial striations on the summit of each lamella. 



The shading ujion this figure is such as to give an incorrect expression to the pi'ojection of the 



concentric lamellae. 



Oriskany sandstone. Cumberland, Marylaiid. 



Spirifer ddodenarius, Hall. 



Figs. 8, 9. Dorsal and cardinal views of a normal adult ; showing general form and external characters. 

 Fig. 10 The interior of a portion of the pedicle-valve ; showing the dental lamellae, the apical callosity and 



the low median septum. 

 Fig. 13. An enlargement of the external surface ; showing the fimbriated lamellae. As in tig. 7 the shading 

 is applied in such a manner as to give an incoriect apjiearance to the lamellae. 



Corniferous limestone. Wtstern New York. 

 Fig. 11. The internal cast of a pedicle-valve ; showing the outline of the muscular area. 

 Fig. 12. The internal cast of a brachial valve. 



Schoharie grit. Scholiarie county, N. T. 

 Figs. 14, 16. Two views of- a specimen doubtfully referred to this species. 



Locality f 



Sl'lRIFKK CUMBERLANDI^, Hilll. 



Fig. 16. An individual of normal proportions, retaining the deltidial covering and showing the concentric 



lamellae. 

 Fig. 17. A partial cast of the interior of a pedicle-valve, retaining the spirals and showing the impression 



of the deep, muscular scars. 

 Fig. 18. Profile of the specimen represented in fig. 16. 



Fig. 19. The interior of a brachial valve ; showing the articulating apparatus and low median ridge. 

 Fig. 20. The interior of an imperfect j)e<licle-valve, retaining the perforated deltidial covering ; showing 



the articulating ai)|)ai-atus and the composition of the muscular area, with a minute foramen 



at the summit of the deltidial plate. 

 Fig. 21. An enlargement of the umbonal portion of the same specimen. 



