130 PALEONTOLOGY OF KENTUCKY. 



length, reaching to the apex of the beak, the others are interpolations and 

 considerably shorter, they reach only to the umbo. The bifurcations on the 

 dorsal valve, and the interpolations on the other one, are so plainly marked 

 that they must be observed at the first glance. The fine radiating striae cover 

 fold and sinus as well as the other part of the valves ; towards the. front their 

 number is increased by interpolation, not by bifurcation. Prof. Hall mentions 

 concentric striae, of which I have not noticed the slightest trace, though I 

 possess a specimen showing the surface-markings most perfectly. 

 ' This species has some similarity with Spir. eudora of the Niagara formation, 

 but it is easily distinguished from the latter by its elevated beak, its peculiar 

 plications, and less gibbosity. 



Formation and Locality. Occurs in the upper strata of the Niagara rocks, in the quarries east of 

 Louisville, Ky., where it is found in well preserved specimens; but it is extremely rare. Less than a dozen 

 of specimens are so far found, which belong either to my own cabinet or to that of the late Dr. James 

 Knapp, of Louisville, Ky., who furnished Prof. Hall with the types for his figures and descriptions. I 

 have never heard of its occurrence at any other place. 



Spirifera radiata. SOWERBY. 



Plate XXIX., figures 13, 14, 15 and 16. 



Spirifer radiatus, Sowerby. Silurian System, p. 637, pi. 12. 

 Delthyris radiatus, Hall. Geol. Kep. 4th Dist. N. Y., p. 1051843. 

 Spirifer radiatus, Hall. Pal. N. Y., Vol. 2, pp. 66 and 2651852. 

 Spirifera radiata, Hall. Ind. llth Kep. of State Geologist, page 296, plate 24, figures 20 to 301881. 



Shell variable in form, sub-triangular, rotund or sub-globose ; valves almost 

 equally convex ; hinge-line considerably less than the greatest width of the 

 shell ; cardinal extremities rounded. 



Ventral valve gibbous, and curving regularly towards the anterior and lateral 

 margins ; greatest convexity above the middle of the valve ; mesial sinus 

 shallow and flat at the bottom, and, extending to the apex, it is rapidly widen- 

 ing towards the front, where it forms a broad extension, the termination of 

 which is only faintly curved. The specimen figured on plate 29 shows, in 

 figures 13 and 14, the termination of the mesial depression and elevation too 

 much curved ; this is not the fault of the draughtsman, but is caused by the 

 form of the specimen, of which said figures are correct copies. Generally the 

 mesial fold is flattened in front, causing the straight termination; but this 

 M-im<*n had the fold rounded to the front, which produced the strongly 

 curved extension. 



The margins of the sinus are pretty well defined in the umbonal region, but 

 from there downwards they are only faintly indie* ^ft. The beak is sometimes 

 considerably elevated above the hinge-line, and on/y slightly curved, as in the 

 specimen figured, while in others the cardinal area is scarcely visible, and the 



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