446 A. W. GRABAU THE SHERBURXE SANDSTONE 



12. CstephaniHall 



This may have a similar ancestry. 



23. Orhiculoidea neglecta Hall 



This is so far known only from the Ithaca group. It may 

 readily be a descendant of one of the regular Hamilton types like 

 0. seneca, with which Hall compares it, or perhaps 0. doria. 



24. Productella liallana Walcott 



This is a species derived from the lowan and farther west 

 Upper Devonic. It occurs in the High Point fauna. At Ithaca 

 it occurs 380 feet above the Sherburne. 



25. Productella speciosa Hall 



This specieS;, like the preceding, may be of western origin. It is 

 not impossible that it is derived from some of the species of the 

 Traverse group. Its derivation from typical Hamilton forms is 

 not, however, excluded. Its young has fewer spines, like some of 

 the smoother mid-Devonic species. It occurs also in the Sanies 

 fauna. 



28. Schizophoria impressa Hall 



This, like all the Middle Devonic schizophorias, seems to be an 

 immigrant from the west, occurring first in the Tully (S. tiil- 

 liensis). It is not characteristic of the typical Hamilton. 



32. Spirifer mesistrialis Hall 



This, according to H. S. Williams,-*^ is a derivative from the 

 Upper Hamilton, S. tullius, a form also characteristic of the Tully. 



33. Spirifer mucronatus var. posteiis 



This is a modification of the ubiquitous S. mucronatus of the 

 Hamilton group. It often shows a median plication in the sinus, 

 as is not infrequently the case in some Traverse group mutations 

 of this species. 



37. Stropheodonta {Leptostrophia) perplana var. nervosa Hall 



This is a derivative of the Hamilton form cliaracterized by the 

 irregular and often noded stria?. The young has the characters of 

 S. perplana.. It sometimes shows strongly mucronate cardinal 

 angles. 



26 BuU. Geol. Soc. Am., vol. 1, p. 491. 



