74 



mian types — some of them belonging to genera not known 

 in rocks older than the Permian — and at the same time re- 

 quested to give us some information respecting the strati- 

 graphical position of the rock from which they were ob- 

 tained. 



Since that time we have received several letters from 

 that gentleman, informing us that the rock from which he 

 obtained these fossils, is about fifty feet in thickness, and 

 reposes upon the Coal measures. He also writes that it 

 consists of alternate beds or layers of the character of the 

 matrix of the fossils (Magnesian limestone), and a reddish 

 brown shale, and that the whole has the aspect of having 

 been deposited in depressions previously worn in the Car- 

 boniferous rocks. 



Having recently received from Dr. J. G. Cooper, a col- 

 lection of fossils from this formation at another locality, 

 which he has kindly given us leave to publish, and Major 

 Hawn having also, as already stated, granted us the same 

 privilege in regard to his collections, we take this method 

 of bringing the matter before the public. 



Amongst the fossils from this rock, we have, in Major 

 Hawn's collections from Smoky Hill fork of Kansas river, 

 as well as in Dr. Cooper's collection from another locality 

 one hundred miles north-east of that, an attenuate Myteloid 

 shell belonging to the genus Myalina, of Koninck, established 

 by him upon Carboniferous species, but well known to occur 

 also in the Permian and more modern formations. This 

 species is rather more slender, but in other respects is not 

 unlike the Permian Myalina accuminata. Another species in 

 the same collection, belongs to the genus Panopaea, also a 

 generic type not known, we believe, below the Permian. 



In addition to the foregoing, there are in Major Hawn's 

 collections, and amongst a few specimens long since obtained 

 by one of us* from the same rock on the Missouri river, op- 

 posite the northern boundary of Missouri (which we had sup- 



*Dr. Hay den. 



I 



