f4 THE NAUTILUS. 



Ohio River drainage. Between the Scioto and the Hocking 

 Rivers is a fairly large stream known as Raccoon Creek. It is 

 now polluted with mine waste and at the time of my visit to it 

 three or four years ago I found no living mollusks in the creek, 

 and only one or two dead Unios. 



East of the Muskingum system is the Mahoning River and 

 Beaver Creek, crossing the Ohio border into Pennsylvania. I 

 know nothing of the Goniobases of these streams, but suspect 

 that if any occur in them it is G. pennsylvanica Pilsbry, the 

 Goniobasis of the upper Ohio rivers. 



The chart of this distribution shows that livescens crosses the 

 northern section of Ohio in the drainage of the Great Lakes and 

 down two streams of the Ohio River drainage. Semicarinata 

 occupies the three largest streams of the Ohio River drainage 

 from the Scioto at about the center to the Great Miami, dis- 

 charging at the southwest corner of the state. 



If we grant that the same laws which have governed the re- 

 peopling of Lake Erie with Naiades have controlled in the case 

 of livescens, this species entered the Maumee River through the 

 Wabash, spread eastward to the Niagara and beyond. It man- 

 aged by means which the geologists might explain to cross 

 the divide between the Cuyahoga and Tuscarawas River, possi- 

 bly thence into the Hocking. 



Other species of Goniobasis than those mentioned have been 

 recognized as occurring in Ohio, and other local races may yet 

 be described, but I feel certain they can all only prove to be 

 descendants of the two parent stocks, livescens and semicarinata. 



SOME LARGE SPECIMENS OF ARGONAUTA. 



BY CHARLES W. JOHNSON. 



The largest species, or the largest example of a species, is 

 always a subject of special interest, both to the biologist and 

 the collector. Individual variation is not fully understood and 

 cannot always be attributed to favorable or unfavorable environ- 

 ment, or the abundance or lack of nutrition. Individual varia- 

 tion has often led to arguments among conchologists as to 



