PLATE XXXV. 
(Figures 1-29 by K. P. Whitfield.) 
Legend: D. 
A. 
F. 
t. 
d. 
X. 
s. 
Deltidial plates. 
Delthyriuni. 
Foramen. 
Teeth. 
Dental lamellae. 
Pedicle-cavity. 
Median septum. 
j. Cardinal process. 
b. Dental sockets. 
c. Crura. 
a. Anteiior adductors, 
a'. Posterior adductors, 
r. Diductors. 
Genus SPIEIFER, Sowekby. 
Page 1. 
Spirifer sulcatus, Hisinger. 
Fig. 1. An individual of normal proportions ; showing the lamellose exterior. 
Fjg.s. 2, 3. Enlai’gements of the central portion of the cardinal area of two examples. The deltidial jilates 
hav'e not united in either specimen, but have attained a more advanced development in fig. 2 
than in fig. 3. 
Fig. 4. Enlargement of the external lamellose surface ; showing the minute pustules on the radial stria- 
tions. 
Niagara group. Lochport, N. Y. 
Spirifer raricostus, Conrad. 
Fig. 5. A brachial view of a specimen of ordinary size. 
Fig. 6. An enlai'gement of the surface of the same specimen ; showing the inequidistant lamellsE. 
Corniferous limestone. Central Neio York. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Spirifer perlamellosus, Hall. 
7. A normal adult shell, retaining the deltidial covering and foramen. 
8. A median longitudinal section of conjoined valves ; showing the dental plates and median septum 
of the pedicle-valve and the crura of the brachial valve. 
9. An enlargement of the external surface ; showing the crowded and radially striated lamellae. 
10. An enlargement of the central portion of the cardinal area, bearing a perforated deltidial covering 
in which the plates are completely coalesced and extend to the beak of the brachial valve. 
11. A similar enlargement from another specimen, having a shorter deltidial covering. 
12. The interior of a pedicle-valve; showing the imperfoi'ate deltidial covering and the median 
septum. 
13. An enlargement of the central portion of a brachial valve ; showing the crura and the peculiar 
bilobed form of the cardinal process lying at the base of the socket-walls. 
Lower Helderberg group. The Heldei'hergs, N. Y. 
Spirifer raricostus, Conrad. 
14. An enlargement of the central portion of the cardinal area; showing its transverse striation and 
the incipient deltidial plates. 
Corniferous limestone. Albany county, N. Y. 
15. An oblique view of the pedicle-valve ; showing the median septum. 
Corniferous limestone. Western New York. 
16. The interior of a pedicle-valve of a small individual; showing the teeth and low septum. 
17. An internal cast of a pedicle-valve ; showing the filling of the rostral cavity, the position of the 
median septum and the impression of the muscular scars. 
Schoharie grit. Albany county, N. Y. 
