154 PALEONTOLOGY OF KENTUCKY. 



identical. Specimens in the collection of the late Dr. James Knapp, marked 

 by Prof. Hall himself as Spir. angusta, can not be distinguished from Spir. 

 segmenta. If his original Spir. angusta are really identical with those marked 

 by him as of the same species in Dr. Knapp' s cabinet, we must consider seg- 

 menta and angusta as belonging to one and the same species. Both are origi- 

 nally described by Prof. Hall in his tenth report on the State Cabinet, in 1857, 

 and it is therefore difficult, if the identity of segmenta and angusta should be 

 proved, to decide which of them ought to be placed among the synonyms. 

 Inasmuch as Spir. segmenta is described in said report on page 131, while the 

 description of Spir. angusta appears on page 164, the name segmenta has pre- 

 cedence over angusta. 



But those specimens marked by Prof. Hall do not at all agree with his 

 figures in the 4th volume of the Pal. of New York, and it is, therefore, possi- 

 ble that he made a mistake in his identification. I have never found a Spirifer 

 in our strata that agreed fully with Hall's figures of Spir. angusta, where the 

 cardinal area inclines so much forward, and where the cardinal extremities are 

 so mucronate. If Spir. angusta holds good as a species, it has, as far as I 

 know, not been found near the Falls of the Ohio. 



Formation and Locality. Spir. segmenta is found in abundance, and as well preserved specimens, 

 in the Coruiierous limestone of Kentucky and Indiana, at and around the Falls of the Ohio river. 



Spirifera varicosa. HALL. 



Plate X., figures 11 to 20, and 23 to 25. 



Spirifer varicosns. Hall. Tenth Rep. on the State Cab., p. 130 1857. 

 Spirifer varicosus, Hall. Description of New Pal. Fossils, p. 90 1857. 

 Spirifera varicosa, Hall. Pal. N. Y., Vol. 4, p. 205, pi. 31. 



Shell somewhat semi-circular or semi- elliptical ; length equalling or less than 

 half the width; hinge- line equal to greatest width of shell, and terminating 

 in salient angles or mucronate extensions. Surface plicated. 



Ventral valve much the more convex ; greatest elevation at the umbo, and 

 regularly curving to the front and to the lateral margins ; mesial sinus strongly 

 defined, rather flat in the bottom ; beak slightly arcuate ; area high, nearly 

 flat below, and slightly concave towards the apex. 



Dorsal valve moderately convex, with a prominent, abruptly elevated mesial 

 fold, which is flattened on the summit, and sometimes slightly depressed along 

 the center ; the beak projecting a little above the hinge-line, and over a narrow 

 area gently incurved. 



The surface is marked by from eight to ten simple and somewhat abruptly 

 elevated plica tions on each side of the mesial fold or sinus; they are crossed 

 by strong lamellose, imbricating lines of growth, which give a varicose charac- 



