PLATE XXXIII— Continued. 

 Fig-. 22. An enlargement of the umbonal portion of the brachial valve represented in li','. !!• ; showing the 

 sti'ucture of the articmlatin;,'- apparatus with more detail, the j'nrtially closed foramen at the 

 apex of the valve, and the low median septnm. 

 Fig. 23. An enlargement of the surface; a portion of the concentric lamella' showing faint i-adial strialions, 

 Oriskany sandstone. Cumbtrland, Maryland. 



SpIRIFEB ARRECTUS, Hill I. 



Fig 24. The exterior of an exfoliated pedicle-valve. 



Fig. 25. The exterioi- of a large brachial valve, retaining a few of the concentric lamellae. 

 Kig. 2tj. The internal oast of a pedicle-valve ; showing the cast of the deep muscular impression. 

 Fig 27. An enlargement of the external surface. This rejiresentation is very imperfect. The exterior of 

 the shell is strongly lamellose, each lamella bearing a series of simple spinules. 

 Oriskany sandstone. Albany county, N. T. 



