368 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 Strepomatide and Unionide of the Ohio 
River, such as Gastrodonta gularis, Omphalina levigata and 
friabilis, Polygyra appressa, obstricta and stenotrema, and prob- 
ably others. Western species extending as far eastward as 
Ohio, are Zonitoides leviusculus, Vallonia parvula, Bifidaria 
holzingert. 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 Unionide 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 
