FOSSILS OF TEtF, SILURIAN AND DEVONIAN ROCKS. 117 



The length of a full grown individual is a little more than three-fourths of 

 an inch, its width about one inch and three- eighths, and its height also about 

 three-fourths of an inch. (Hall.) 



After the foregoing description Prof. Hall makes the following statement : 

 "I have before me more than a dozen specimens from near the Falls of 

 the Ohio, or from Charlestown Landing, among which there is very little varia- 

 tion in the general features." 



If those specimens did not show great variations, they must have formed a 

 picked lot. I have before me more than an hundred shells of this species, 

 which I could easily divide into at least live different groups. The extreme 

 form of each group is so pronounced in its features, and so greatly different 

 from the extreme form of other groups, that they, by themselves, would con- 

 stitute good species ; but the intermediate forms connect all these groups to 

 one single species. 



Formation and Locality. Found in great abundance, and well preserved, in the Devonian limestone 

 in Kentucky and Indiana, near and at the Falls of the Ohio. Some of the specimens have preserved the 

 internal spiral coils in almost perfect condition, as may be seen by plate 6, figures 21 and 22. 



Spirifera euruteines, var. fornacula. HALL. 



Plate VI., figures 8, 10, 18, 19 and 20. 

 Spirifera. euruteines, var. jornacula, Hall. Pal. N. Y., Vol. IV., page 211, pi. 31, figures 11, 12 and 13. 



Prof. Hall, in describing this variety, remarks that it possesses the essential 

 characters of Spir. euruteines, and points out, as the only difference from that 

 species, that its area is a little more arcuate in the upper part. Those figured 

 by "me here are of the type which is generally considered as fornacula by all 

 the geologists living in the cities around the Falls of the Ohio. The strong 

 curvature of the whole cardinal area is their only marked characteristic. 



Formation and | Locality. Associated with the preceding species in the Devonian limestone in 

 Kentucky and Indiana, around the Falls of the Ohio. 



Spirifera foggi N.BP. 



Plate XXXII., figures 28, 29, 30 and 31. 



Shell of medium size ; sub-circular sub-oval or sub-elliptical ; very ventn- 

 cose or gibbous ; hinge-line greatly less than width of shell ; cardinal extremi- 

 ties rounded. Surface plicated. 



Ventral valve ventricose in young specimens, becoming gibbous in old ones ; 

 greatest convexity a little above the middle of the valve, from where it slopes 

 in a gentle regular curve to the front, but abruptly to the cardino-lateral mar- 

 gins ; a mesial sinus extends from beak to front, well defined in its whole 



