PLATE XXIX. 



(Figures 1-5, 7-17 by E. Emmons; 6 bj 11. P. WniTFiELn.) 



Genus SPIRIFER, Sowerby. 



Page ]. 

 Sl'IKIFER ARENOSUS, Coiinul. 



Fifj. I. An indiviilual with most of the brachial valve removed ; showing- the brachial cones encrusted 

 with silica. 



Fig. 2. An intei-nal silicious cast from which the calcareou.s spiral ribbon has been nalui-ally removed, ex- 

 hibiting- the casts of the conical I'Hvilies. 



Fig-. 3. A silicified specimen ; showing: a portion of the spiral cones. 



Fig. 4. A larger example, slightly reconstructed from a silicified interior ; showing the long crura, the 

 disconnected .jugal pi-ocesses, the form of the primai-y lamelb-e and the shape ami direction of 

 the cones. 



Oriskany sandstone. Cumberland, Maryland. 



SriRIFER AUDACULU.S, Coilivul. 

 See Plate 24. 

 Fig. 5. A preparation, showing the character of the brachidium. (c.) 

 Hamilton group. Canandaiffua Lake, N. Y. 



Spirlfer IIungerfordi, Hall. 



Fig. 6. A specimen with the brachial valve removed ; showing the form of the brachidium. 

 Uppei- Devonian. Rochford, Iowa. 



Spirtfer gregarius, Clapp. 



Fig. 7. A preparation, showing one of the spiral cones, with its jugal process and crus. X 2. (c.) 

 Corniferous limestone. Falls of the Ohio. 



Spirifer mucronatus, Conrad. 



Fig. 8. A preparation, showing the form and size of the pi-iraary lamellse aiul the long, tapering spiral 

 cones, (c.) 



Hamilton group. Canandaigua Lake, N. Y. 



Spirifer granulosus, Comad. 



See Plate 23. 

 Figs. 9, 10. Two views of a xireparation, showing the form and direction of one of the spirals, (c.) 



Hamilton group. Petosky, Michigan. 

 Figs. 11, 12. A preparation, showing the length of the crura, jugal processes and the narrow, small primary 

 lamellae, (c.) 



Hamilton group. Caiiandaigiia Lake, N. Y. 



Spirifer ligus, Owen. 



See Plate 22. 

 Fig. 13. A prepai-ation, showing the crural bases, their .attachment to the crura, and the form of the spiral 

 cones which appear to have been somewhat disturbed toward the apices, (c.) 

 Hamilton group. Independence, Iowa. 



Spirifer subumbona, Hall. 

 Fig. 14. A prepai-ation, showing the lax coil of the spiral. X 4. (o.) 

 Hamilton gi-oup. Western New York. 



