PI.ATK XXXIII— ConUnaed. 

 Fig'. 22. An enlar^ment of the nmbonal jiortion of the brachial valve represented in tiur. 19 ; showing the 

 structure of the articulating apparatus with more detail, the partially closed foi-amen at the 

 apex of the valve, and the low median seiitum. 

 ¥ig. 23. An enlargement of the surface; a portion of the concentric lamellse showing faint radial striations. 

 Oriakany sandstone. Cuinberland, Maryland. 



SpIRIFER 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. 

 Fig. 26. 'I'he internal cast of a pedicle-valve ; showing the cast of the deep muscular impression. 

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

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

 Oriskany sandstone. Albany county, N. T. 



