EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 83 



convex. Usually they are of considerable length fore and aft, but specimens 

 are found, showing no apparent distortion, that are quite narrow and elon- 

 gate. The hinge is the longest measurement of the shell and the ribs 

 number from 7 to 1 1 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 Oriskany classed as S. m u r c h i s o n i, where 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. cit7\ 

 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. antarcticus, S. chuquisaca, S. orbignyi 

 and S. cap e n s i s, from the Falkland Islands, Bolivia and South Africa 

 and that others, principally the smaller forms, express the local value of 

 S. m u rch i s o n i. There are excellent reasons for these views, and though 

 shells like S. p r i m a cvus var. atlanticus are apparently absent from 

 the New York province yet there is no wide divergence between them and 

 the larger examples of S. murchisoni. It will be understood that a 

 proper interpretation of the congeries passing as S. murchisoni in the 

 Oriskany is possible only in terms of well defined localized expressions; at 

 the same time as between the northern and southern species there are dis- 

 tinctive features in sculpture, S . antarcticus for example being a radi- 

 ately striated shell and therefore not in harmony with the group of S. 

 murchisoni which carries a fimbriate exterior. These differences the 

 author has discussed elsewhere. 



Localities. Abundant at Baker Brook and Tomhegan points, Moose- 

 head lake, Me. 



Spirifer arenosus (Conrad) 



Plate iq, figures 1-4 

 See pt 1, p. 17Q 



Entirely characteristic examples of this species as it occurs in the 

 Oriskany sandstone of central New York, though quite uniformly of 

 smaller size, are very abundant at Cunningham's cam]). In these sandstones 

 the habit expressed in form and size is persistent in all specimens. 



A smaller expression of the species occurs in the more compact 

 sandstone in Parlin Pond township north of Bean brook. 



