380 Procci'diiif/s of tJir Ohio State .Icadcviiy of Science. 



he would have adopted Whit field's and added .V. iiicrebesceiis 

 to the hitter's list. 



Hall's inahility to separate .V. keokiik var. (St. Louis lime- 

 stone, 1858) from .S". keokiik (Keokuk limestone, 1858) seems 

 espeeially signihcant. S. keokiik appears to represent one ex- 

 treme, the short hinge line, and S. iiicrebesccns ( Kaskaskia lime- 

 stone, 1858) the other extreme, the long hinge line, of an other- 

 wise very similar series of specimens. Between the two is 

 5". keokiik var. with specimens exhihiting hoth long and short 

 hinge lines. The ones with the long hinge lines might as well 

 have heen selected as the type in this case and the name S. 

 increbesceiis var. applied rather than ^. keokiik var. To he 

 sure, it is not difficult to identifv specimens of one extreme as 

 .S'. keokiik and those of the other as S. increbesceiis, 1)ut what 

 is to be done with the intermediate forms wdiich fall as readily' 

 under one species as the other? 



Jtist why Spirifer of^iiniis (Coal Measures of Ohio, Mary- 

 land and Iowa, 1858) should have been originaly referred to 

 S. rockyinoiitaiii ( Moutain limestone of New ^tlexico, 1858) 

 rather than to .S\ keokiik. which it more closely resembles, is not 

 clear. ,S. pi in us is imdoubtedly an ofifspring of one of the 

 Mississipj:)ian forms, and more probably one from the adjacent 

 Mississippian series rather than one from the western ]\Iis- 

 sissippian. 



If any specific division is to be made in the above forms 

 it would seem to fall between .S". rock\-niontani ( 1858) on the 

 one hand and 5. keokiik (1858), 6\ keokiik var. (1858), 5'. 

 incrcbescens (1858), and .S". opiums (1858) on the other. This, 

 of course, would give specific rank to the first and second and 

 make all of the rest synonyms of the second. Should no divi- 

 sion be deemed advisable then all of Hall's species become syn- 

 onyms of Spirifer rockyiuoutauiis Marcou (1858). 



In the lower half of the Maxville limestone are found speci- 

 mens of Spirifer which resemble very closely the figures of S. 

 rockyiuoniauiis Marcou (especially 4 c-e ) in two respects: 

 first, the ])lications are small and sharply angular ; and second, 



