PLATE XXIX. 



(Flcura* 1-A, 7-17 by E. Emmons; 6 by B. P. Whitfiblo.) 



Genus SPIKIFER, Sowerby. 



rago I, 



Spiuifer arenosus, Conrad. 



¥ig. I. An individual with most of tlie brachial valve removed ; showing' the brachial cones encrusted 

 with silica. 



Fig. 2. An internal silicious castr from which the calcareous spiral ribbon has been naturally removed, ex- 

 hibiting the casta of the conical cavities. 



Fijf. 3. A silicified 8i>ecinien ; 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 processes, the form of the primary lamellie and the shape and direction of 

 the cones. 



Oriskany sandstone. Cumberland, Maryland. 



Spikifer audaculus, Connid. 



See Plate 24. 

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

 Hamilton group. Canandaigua Lake, N. Y. 



SpiKifER IIungeufokdi, H.lll. 



Fig. 6. A specimen with the brachial valve i-emoved ; showing the form of the brachidium. 

 Upper Devonian. Bockford, lotoa. 



Spirifer GREGARIUS, Cliipp. 



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

 Corniferous limestone. Falls of the Ohio. 



Spirifer mucronatus, Coin-ad. 



Fig. 8. A preparation, showing the form and size of the primary lamellse and the long, tapering spiral 

 conep. (c.) 



Hamilton group. CaTiandaiffita Lake, iV. Y. 



Spirifer granulosus, Conrad. 



See Plate 23. 

 Figs. 9, 10. Two views of a preparation, 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 nan-ow, small primary 

 lamells. (c.) 



Hamilton group. Catiandaigiia Lake, N. T. 



Spirifer ligus, Owen. 

 See Plate 22. 

 Fig. 13. A preparation, showing the crural bases, their attachn.ent to the cmra, and the form of the spiral 

 cones which api>ear to have been somewhat disturbed toward the apices, (c.) 

 Hamilton group. Independence, Iowa. 



Spirifer subumbona, Hall. 



Fig. 14. A preparation, showing the lax coil of the spiral. X 4. (c.) 

 Hamilton group. Western New York. 



