3(38 OHIO STATE ACADEMY OF SCIENCE. 



features of special interest. The northern part of the state is in 

 the drainage of the upper St. Lawrence River, which has fresh- 

 water forms of the Atlantic Sub-province mixed with some of 

 the Mississippi drainage. Also there are a number of boreal and 

 circumboreal species. The Northeast, the so-called Appa- 

 lachian Corner, seems to be inhabited by some specifically 

 Appalachian snails also, e. g. Gastrodonta lasmodon and collisella, 

 Hyalina lamellidens and an unidentified Hyalina; and more may 

 be found. The southern part of the state has some southern 

 forms, outside of the Strepomatidae and Unionidas of the Ohio 

 River, such as Gastrodonta gularis, Omphalina laevigata and 

 friabilis, Polygyra appressa, obstricta and stenotrenia, and prob- 

 ably others. Western species extending as far eastward as 

 Ohio, are Zonitoides lavius cuius , Vallonia parvula, Bifidarin 

 holzingeri. The distribution of all of these species, and even- 

 tually others, should be ascertained more exactly. 



But it must be understood that our mollusca are rapidly and 

 considerably decreasing in numbers, by deforestation and 

 cultivation of the land, draining of lakes, ponds and swamps, 

 and consequent disappearance of springs, brooks and smaller 

 creeks, or their being dry during a large part of the year, result- 

 ing in the disappearance of mollusca. In the rivers and larger 

 creeks, the water comes to its lowest stages, with sudden floods 

 rapidly receding. Shade, as a protection from insolation, is 

 taken off by cutting down the trees on the banks of water 

 courses. The canals, which were great routes for mollusca, are 

 more and more neglected, and partly abandoned. To this 

 comes the contamination of waters by city sewage and factory 

 refuse, and already a number of rivers are barren of life or 

 rapidly approaching that stage. These factors certainly affect all 

 groups of fresh water animals, not only the mollusca. And of 

 late years, the Unionidae are destroyed in wholesale slaughter, 

 by the shell and pearl hunters. Thus, not only the number of 

 individuals is rapidly reduced, but many species are threatened 

 with extinction over large tracts of the territory. Therefore it is 

 imperative that we take a careful inventory of our fauna as 

 rapidly as possible. 



To the main catalogue of recent mollusca are added a few 

 supplements: a list of species not or little known up to recent 

 years, mistaken for or mixed up with others; a list of species not 

 yet known to occur in the state, but probably to be found; lists 

 of fossils collected. 



With respect to the general catalogue, a few remarks may 

 be in place. Of common, and widely distributed species, of which 

 Ohio is within the area of general distribution, it was thought 



