i 



PLATE XXX. 



(ngaiw 1-17, 1», so, tS-n, so by R. P. WHITPIBLD; 18, 21, 22, 28, 29 by F. B. Hbbk.) 



L«gen<l : A. CanlinHl Hrea. 

 »'. Inner division. 

 »". Outer division. 

 .^. Dellhyriurn. 

 D. Deltidium. 



t. Teeth. 



j. Cardinal pi-oceas. 

 b. Dental sockets 

 a. Ailductor scars. 

 r. Diductor scars. 



Genus SPIRIFER, Sowekby. 



I'ago 1, 

 SpIHIFEK OONCINNUS, Hllll. 



Fig. 1. A large individual ; showing the incipient plications on the fold. 

 Fig, 2. Cardinal area of the pedicle-valve retaining the deltidial covering. 

 Lower Helderberg group. TTie Belderbergi, N. T. 



Spirifer AREN08U8, Coiir.id. 



See Plate 29. 

 Fig. 3. An entire individual, of small size, compared with the New York examples, but near normal pro- 

 jwrtions for this locality. 



Oriskany sandstone. Cwtnberland, Maryland. 

 Pig. 4. The internal cast of a pedicle-valve ; showing the gi-eat diductor scars, enclosing the adductors. 

 Fig. 6. The central cardinal portion of an internal cast of the brachial valve; showing the form of the 



cardinal process and the size of the adductor scars. X H- 

 Pig. 6. The articulating a]iparatus of the brachial valve. 



Fig. 7. The cardinal area of a pedicle-valve ; showing the deltidial covering and teeth. 

 Oriskany sandstone. Eastern New York. 



Spirifer unicus, Hall (^S. arenosus, Conrad). 



Pig. 8. The original specimen ; showing the plicated sinus. 



Upper Helderberg group. Clarence Hollow, N. T. 



Spiuifeu Grieui, Hall. 

 Pigs. 9-11. Views of a normal individual. 



Fig. 12. The brachial valve of a larger shell with stronger plications on the fold. 

 Pig. 13. Front view of the same specimen. 



Upper Helderberg group. Ohio. 



Spirifer disjunctos, Soweiby. 



Fig. 14. The internal cast of a pedicle-valve with alate cardinal extremities ; showing the size and composi- 

 tion of the muscular area. 



Chemung group. Meadville, Penn. 

 Fig. 15. A small, nearly entire individual, retaining the shell. 

 Fig. 17. The internal cast of a small, short-winged pedicle-valve. 



Sandstones of the Chemung gi-oup. Western New York. 



Spirifer disjunctus, Soweiby, var. sulcifer, var. iiov. 



Pig. 16. The internal cast of a brachial valve ; showing the sulcus on the plicated median fold. 

 Chemung group. Near Olean, N. T. 



Spirifer Wiiitneyi, Hall. 



Pig. 18. An individual of normal size, but rather short hinge. 

 Pig. 19. The interior of a brachial valve. 



Chemung group. Bockford, Iowa. 



