THE NAUTILUS. 21 



Michigan, on the south shore, nor at Isle Royale, at the western end 

 of the lake. On the other hand, Lampsilis luteola, a characteristic 

 species of the Mississippian fauna, was common at Isle Royale, and 

 is known to extend along the south shore as far at least as Marquette 

 county, and is represented on the north shore by a closely allied form, 

 Lampsilis super ioriensis, from the Michipicoten River. 



The fauna of the Atlantic region, in its northern portion, is a very 

 meagre one. As represented in the New England States, and in a 

 general way as far south as Mason and Dixon's Line, it consists of 

 only thirteen species, but south of that, and increasingly so towards 

 the extreme south, it becomes a wonderfully varied fauna, in which 

 the specific lines in many of the groups seem to be almost wholly 

 obliterated. As an example of this, it might be mentioned that, in 

 the case of Unio complanatus Dill., while Dr. Lea, in the northern 

 portion of the region, recognized only the one species, in the southern 

 portion he described no less than forty-six forms as distinct species, 

 which Simpson in his synopsis has referred to the typical form as 

 synonyms. 



Taking the Atlantic fauna as represented in New England as the 

 basis of comparison with that of the Great Lakes, as found in Lake 

 Erie and the Detroit River, we find the two faunas represented by 

 the following list : 



LAKE ERIE. NEW ENGLAND. 



Truncilla 



triquetra triangularis Bar. 



sulcata delicata Simpson. 



perplexa rangiana Lea. 

 Micromya fabalis Lea. 

 Lampsilis Lampsilis 



ventricosa canadensis Lea. cariosa Say. 



ochracea Say. 



multiradiata Lea. 



luteola rosacea DeKay. radiata Gmel. 



recta sageri Con. 



nasuta Say. nasula Say. 



iris Lea. 



parva Bar. 



alata Say. 



