56 THE NAUTILUS. 



" Tritonshornschnecke {Charonia Nob.; sonst : Tritoniuni)." Then 

 follows a generic diagnosis and there is given a description of the 

 species " Ch. tritonis Nob." 



I conclude then, if no name exists prior to Gistel, 1848, that 

 Charonia Gistel should be the generic name to be used for .Murex 

 tritonis Linn 6. 



Two further points require notice : To those unable to refer to 

 Gistel a second Charonia might prove troublesome, as on p. 178 with 

 a quaint carelessness he proposes Charonia for an Acaleph. 



The family name to be used for the Tritons I would suggest should 

 be Cymatiidse, based upon the oldest genus name in the family. 

 Basing the family name upon the supposed typical genus seems a 

 quite unscientific method, as so much would depend upon the per- 

 sonal equation ; speaking for myself I would have considered Murex 

 tritonis Linne, a quite atypical member of the family, glancing over 

 the whole of the molluscs at present associated in it. 



THE UNIONS FAUNA OF THE GREAT LAKES. 



BY BRYANT WALKER, SC. D. 



(Continued from page ^7.) 



IV. 



From what has already been said, it would seem to be clear that 

 there is not any possibility that the present fauna of Lake Erie 

 could be a relict fauna that persisted there during the glacial period. 

 The entire region was covered by the ice and the entire configura- 

 tion of the land was overwhelmed, blotted out, and the system of 

 drainage was entirely changed by the drift deposited on the retreat 

 of the ice. That under the enormous thickness of the ice cap 

 throughout that entire area, there could have been any survival of a 

 Naiad fauna seems absolutely impossible. But there are other facts, 

 which show that the representatives now found in the Great Lake 

 region of the Mississippi and Ohio faunas, are the results of a post- 

 glacial invasion and that the modifications that have taken place in 

 their size, shape, and appearance have been brought about by en- 

 vironmental changes since glacial times. The entire Lower Penin- 

 sula of Michigan was in the glaciated area. If the present fauna of 

 that area has been derived from a survival in the Great Lakes, or in 



