PLATE XXXIII. 
(Figures 1-23, 27 by R. P. Whitfield; 24-26 by F. B. Meek.) 
Legend: A. 
Cardinal area. 
f. 
Fissure at base of dental sockets 
D. 
Deltidium. 
(brachial valve). 
f. 
Foi-amen. 
Rostral callosity. 
t. 
Teeth. 
b. 
Dental sockets. 
s. 
Median septum. 
c. 
Ci'ura. 
s'. 
Delthyrial callosity. 
sp. 
Spirals. 
Dg. 
Margins of delthyrium (bi-achial 
a. 
Adductor scars. 
valve). 
r. 
Diductor scars. 
Genus SPIKIFER, Sowerby. 
Page I. 
Spirifer tribults, Hull. 
Fig. 1. The exterior of a brachial valve of an average example; showing the laniellose sui'face. 
Fig. 2. The exterior of a brachial valve. 
Fig. 3. The interior of a pedicle-valve ; showing the character of the muscular area. 
Fig. 4. k. cardinal view of conjoined valves ; showing the elevation of the area. 
Oi-iskany sandstone. Cumberland, Maryland. 
Spirifer submucronatus, IImU. 
The exterior of a normal example, retaining the deltidial covering and showing the foramen 
An enlargement of the cardinal portion of the same specimen ; showing the foramen at its 
summit. 
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 incorrect expression to the projection of the 
concentric lamellse. 
Oriskany sandstone. Cumberland, Maryland. 
Spirifer ueodenarius, Hull. 
Figs. 8, 9. Dorsal and cardinal views of a normal adult; showing general form and external chai'acters. 
Fig. 10 The interior of a portion of the pedicle-valve ; showing the dental lamellie, the aiiical callosity and 
the low median septum. 
Fig. 13. An enlargement of the external surface ; showing the fimbiiated lamellae. As in fig. 7 the shading 
is applied in such a manner as to give an incori ect appearance to the lamellae. 
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 s^iecimen doubtfully referred to this species. 
Locality f 
Fig. 5. 
Fig. 6. 
Fig. 7. 
Spirifer Cumberlandue, Hull. 
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 pedicle-valve, retaining the perforated deltidial covering; showing 
the articulating apparatus and the composition of the muscular area, with a minute foramen 
at the summit of the deltidial plate. 
Fig. 21. An enlai’gement of the umbonal portion of the same specimen. 
