8 THE NAUTILUS. 



marginalis Lamarck. The failure to recognize this well-defined 

 genus by most subsequent authors is a very remarkable fact. 



In the preparation of the above remarks I am indebted in a very 

 large degree to my friend Dr. A. E. Ortmann. 



MOLLTJSZS FROM MAGICIAN LAKE, CASS AND VAN BUREN COUNTIES, 



MICHIGAN. 



BY FRANK C. BAKER. 



Magician Lake lies between Van Buren County on the north and 

 Cass County on the south. It is about two and a half miles long 

 and half a mile wide. The banks on the north border are high but 

 on the south, east and west they are for the most part low and 

 swampy. The lake occupies an elongated depression in the Wis- 

 consin drift and contains four deep holes, 40 to 60 feet in depth. 

 The shores are shallow and shelving, and, with the exception of one 

 or two short intervals, one may wade entirely around the lake. The 

 outlet is at the southeast side (known as Silver Creek), and empties 

 into the West branch of Dowagiac Creek, which drains into the St. 

 Joseph River, a Lake Michigan stream. The migrations of the mol- 

 lusks have probably been largely by the way of the St. Joseph, 

 although some of the species may have reached this spot in post- 

 glacial time via the Kankakee-St. Joseph portage ; but the fauna as 

 a whole probably reached these lakes by way of the Chicago outlet 

 when Lake Michigan was in the Lake Chicago stage. It is evident 

 that Magician Lake was once much higher, with a large, wide out- 

 let, for high terraces may be seen on the south, and also bordering 

 tlie outlet. Ancient marl beds exist, now covered by three feet of 

 peat, containing mollusks of a colder climate, attesting the ancient 

 occupancy of this lake by icy waters. 



Mollusks were notably abundant in individuals and species. The 

 species are listed by ecological regions. My thanks are due to Dr. 

 Herman S. Pepoon for assistance in collecting much of the material. 



Beach debris South Shore, all dead shells. 



Alasmidonta calceola (Lea). Planorbis antrosus Conrad. 



Anodonta grandis footiana Lea. Planorbis antrosus angistomus 

 Lampsilis luteola (Lam.). Hald.. 



Sphaerium simile (Say). Planorbis parvus Say. 



