46 NEW YOEK STATE MUSEUM 



The exterior of the shell, preserved in part on one silicified speci- 

 men, bears low and distant radial striae, which are crossed by very fine 

 and crowded concentric lines. Even with our present imperfect knowl- 

 edge the species is clearly distinguished from all known Meristellas, 

 but it is still far from certain that the shell is to be referrrd to this 

 genus. 



Spirifer arenosus Conrad 



1892. Spirifer arenosus Clarke, op. cit. p. 413 



For figures see Paleontology of New York. v. 3, pi. 98, 99, 100; 

 v. 8, pt. 2, pi. 29, fig. 1-4; 30, fig. 3-7 



Specimens of this characteristic Oriskany shell are not at all 

 uncommon here and attain the considerable size and transverse form of 

 the species as it occurs in the higher beds of this state. At Cum- 

 berland Md., and at Cayuga Out., the species is generally much 

 shorter on the hinge and more elongate medially, but this expression 

 has not been observed among the specimens from Becraft mountain. 



No complete account has ever been given of the nature of the 

 surface configuration of this shell, and some of the fine external molds 

 from the decomposed silicious limestone show the characters with exac- 

 titude. The plications are broad and distinctly flattened above, with 

 very narrow interspaces, and the grooves bear the finest radial striations 

 which are not interrupted by concentric lines. This is such a char- 

 acter as is seen on many of the upper Siluric Spirifers, but is not 

 usual among the Ape rtu rati till after the close of the Devonic. 



Spirifer murchisoni Castelnau 



Plate 6, flg. 26-SO 



1843. Spirifer murchisoni Castelnau. Essai syst. silur. de VAmer. septentr. 

 p. 41, P l. 12, fig. 1,2 



1859. Spirifer arrectus Hall. Paleontology of New York. 3 : 422, pi. 97, fig. 

 1,2 



1892. Spirifer arrectus Clarke, op. cit. p. 413 



Characteristic specimens are very abundant throughout these beds. 

 External molds display very perfectly the nature of the surface, which 

 has never been quite accurately given. The broad, subangular ribs are 



