SOME NEW bIiVO.s"IC FOSSILS 



26l 



rather direct and not convex. Usually they are of considerable 

 length fore and aft but specimens are found showing no apparent 

 distortion that are quite narrow and elongate. The hinge is the 

 longest measurement of the shell and the ribs number from 7 to 

 11 on each lateral slope, the smaller number prevailing in the usual 

 preservation. It may be noted that the first pair of ribs bounding 

 the sinus is the highest as this is in contrast to some specimens 

 of the. New York Oriskanv classed as S. murchisoni, where 



Spirifer primaevus 



atlanticus 



the first pair is lower than the second. A comparison of these 

 specimens with those referred to S. arrectus of the Oriskany 

 by Hall and well illustrated in the work cited, shows that 

 there is a close approach in structure among the larger forms of 

 those. In a previous publication [N. Y. State Mus. Mem. op. cit.] 

 I have referred to the probability that the S. murchisoni of 

 the New York Oriskany is an unstable form putting on the aspect 

 now of one and now of another species elsewhere localized. Scupin 

 has with more detail pointed out this condition suggesting that 

 some of Hall's drawings are of forms equivalent to S. antarc- 

 ticus, S. chuquisaca, S. orbignyi and S. c a p e n s i s, 



