PLATE XXXIII. 



(Figures 1-23, 27 by R. 1". WiiiTriELD; 2l-'2(; liy F. B. Mkkk.) 



Legend : A. Cardinal area. 

 D. Deltidium. 

 f. Foramen, 

 t. Teetli. 



s. Median sejitum. 

 s'. Deltliyrial callosity. 

 D}f. Marj,'iiis of deUliyrium (brachial 

 valve). 



Genus SPIRIFER, Sowerby. 



l»a;;e 1. 



Spirifer tkibulis, I hill. 



Fig-. 1. The exterior of a brachial valve of an average example; showing the lamellose surface. 

 Fig. 2. The exterior of a brachial valve. 



Fig. 3. The interior of a i)eilicle-valve ; showing the character of the muscular area. 

 Fig. 4. k cardinal view of conjoined valves ; showing the elevation of the area. 

 Oi'iskany saii<lstone. Cumherland, Maryland. 



SriUlFER SUBMUCRONATUS, ILlll. 



Fig. .'). The extei-ior of a normal example, retaining the deltidial covering and showing the foramen 

 Fig. B. An enlargement of the cardinal 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 upon this figure is such as to give an incori-ect expression to the projection of the 



concentric lamellae. 



Oriskany sandstone. Cumberland, Marylatid. 



Spirifer DUOUENARIUS, Ililll. 



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 himella% the aiiical callosity and 



the low median septum. 

 Fig. 13. An enlargement of the external surface ; showing the timbi-iated lamella;. As m tig. 7 the shading 

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



Corniferous limestone. Western 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. Schoharie county, N. Y. 

 Figs. 14, 15. Two views of- a specimen doubtfully referred to this species. 



Locality f 



iSpIRIFER CUMBERLANDI.E, llull. 



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



lamelke. 

 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. IS. 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 imjierfect pedicle-valve, retaining the perforated deltidial covering; showing 



the articulating ajiparatu-s and the composition of tlie muscidar area, with a minute foramen 



at the summit of the deltidial jilate. 

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



