78 IOWA ACADEMY OF SCIENCES. 



rian some of the shells attained huge proportions, but with the 

 general decline of the group the later ones have heretofore 

 seemed to rapidly become dwarfed until only small, unimportant 

 individuals were recorded after the Devonian. In the Carbon- 

 iferous a few dimunitive species have been described, most of 

 them but a few inches in length. In the coal measures of the 

 Mississippi basin the remains found were of rather rare occur- 



FiGUBE i. Section of Orthoceras fanslerensis. 



rence, imperfectly preserved and of very small size. Seldom 

 did the shells exceed six inches in length and half an inch in 

 diameter. 



Of late years, however, some unusually fine material has 

 been obtained in the black shales of the lower coal measures in 

 the vicinity of Des Moines, Iowa. Several of these shells were 

 so large as to excite considerable wonderment. Some were 

 over two feet long and one inch in diameter at the larger end. 

 These were thought to be giants of their kind and day. But 

 these are small, and all the other Carboniferous species are 

 mere pigmies by the side of the recently found shell from the 

 coal mines of Fansler. The species is 0. fanslerensis, and the 

 unique specimen here described was obtained by Mr. M. G. 

 Thomas, state mine inspector. 



