20 THE NAUTILUS. 



DISTRIBUTION OF UNIONID^ IN THE THREE RIVERS, 

 MAHONING, CUYAHOGA AND TUSCARAWAS. 



BY GEO. W. DEAN, KENT, OHIO. 



The table given below, while making no pretense to absolute ac- 

 curacy, is a fair approximation of the distribution of Unionidse in the 

 thi'ee largest rivers and their tributaries in northeastern Ohio. Al- 

 though they afford us no peculiar species, unless it be the Unio Kirt- 

 landiana Lea of the Mahoning River, they still present some points 

 of interest. The reader must bear in mind that species are not found 

 equally distributed. Some may be found almost anywhere and 

 othei's at only one place in a whole river. The Mahoning and 

 Tuscarawas Rivers are tributaries of the Ohio; the first through the 

 Beaver, the latter through the Muskingum. The Cuyahoga rises 

 about thirty-five miles east of Cleveland and empties into Lake Erie 

 at that city. Its course is southwest to within two or three miles of 

 Akron from which it is almost due north to its mouth. Through this 

 valley runs the Ohio canal, and this canal connects this river with 

 the Tuscarawas by a rise that required sixteen locks, the whole dis- 

 tance between the two rivers being about six or seven miles. It will 

 be seen by the following tabular statement that Unio ligamentmus, 

 rectus, rubiginosus and others are common to the Tuscarawas and 

 lower Cuyahoga, and entirely absent in the ]\Iahoning and upper 

 Cuyahoga. Above the connection of the Cuyahoga with the canal 

 are several falls above which are found only five or six species, but 

 below there the number is largely increased by those named above and 

 a number of other Tuscarawas forms. The interesting question pre- 

 sented is, have these Tuscarawas forms been introduced through the 

 canal during its fifty or sixty years of existence ? A list of the forms 

 found in streams that empty into Lake Erie, and have no connection 

 by canal or otherwise with the Ohio, might throw some light upon 

 the subject. In conclusion I will say that geographical distribution 

 is of paramount importance to the conchologist and collector, and 

 the least contribution to the limited knowledge of the subject we have 

 at present ought to be welcomed. 



