ier 
Review of Geinitz on the rocks and fossils of Nebraska. 323 
regard to specific and generic distinctions, are such as to materi- 
ally detract from the value of his paleontological conclusions in 
a case like that under consideration. The fact that he has un- 
questionably identified specifically, with European forms, several 
ebraska fossils belonging to entirely different genera, and in 
some instances different families, shows conclusively, that if he 
has ept pace with the recent advances made in conchology and 
other departments of natural history, he has not, in this instance 
at least, brought to bear that degree of exactness of discrimina- 
_ tion the present state of zoological science shows to be absolute- 
ag ly necessary, before we can hope to arrive at sound conclusions 
_ I paleontology. : 
se necessity for great care in identifying species and genera 
of shells, has of late years been forcibly illustrated by various 
anatomical researches, but particularly by the results of the val- 
uable investigations of the lingual dentition of the Gasteropoda, 
made by Loven, Troschel, and others, in Europe, and Dr. Stimp- 
son, Mr. Morse, and others, in this country, by which means 
forms long regarded as specifically identical havé been found to 
be quite distinct, and so in regard to the genera and higher 
groups. A case, however, coming more directly home to paleon- 
tologists and geologists, is that in which recent microscopical in- 
vestigations have rendered it probable that a form, until very re- 
cently regarded by the highest living authorities as the common 
Spirifer cuspidatus of Sowerby, is not only specifically, but even 
gen 
__tristic Coal-measure fossils occur in the same beds containing 
__ these few Permian types, while the latter, including the so-called _ 
Monotis, the Bakevellias, Pleurophorus, Schizodus, &c., are also occa- 
_ Slonally met with far below, in unquestionable and acknowledged _ 
-_,* See Proceed. Acad. Nat, Sci. Philad., Dec. 1865 
