THE NAUTILUS. 89 
In the upper reaches we have Io fluviatilis, 100 miles lower 
down we have I. spinosa, I. turrita, and I. brevis. I have collected 
many thousands of these Io’s: spinosa is the most abundant form ; 
then, after picking out a few turrita and brevis there are always a 
large proportion that might fit one place as well as another; there- 
fore I would call them all spinosa, more or less developed by local 
causes. Pleurocera sycamorense in one stream becomes P. estabrookii 
in another, and P. unicale ina third. Goniobasis sulcosa in a brook, 
becomes G. arachnoidea in a creek. Pleurocera parvum and P. 
Lyoni in a creek in the mountains, become P. fastigiatum in large 
streams. Dr. Lewis regarded Goniobasis livescens and G. niagarensis 
the same, and I don’t see why Pleurocera curtum and P. conicum 
should need different names; and when it comes to the Strephobasis 
I don’t want to name them.” Such is the opinion of one who has 
spent many years of her life in exhaustive research and study among 
the Molluses of Tennessee. And when a like thorough search and 
comparison of all the species of North America has been made I pre- 
dict that there will be a wholesale addition to the list of our syn- 
onyms. No doubt in a number of the cases which Miss Law cites 
the difference between selected specimens was great enough to 
warrant separating them and giving them names, but the trouble 
was that intermediate forms of every degree were found, which com- 
pletely connected them; and asin so many other cases this variation 
was produced by circumstances. 
Now species founded on trivial characters, or those which in- 
sensibly merge into others cannot stand. I fully agree with my 
friend Dr. Singley of Giddings, Texas, who says that he wants species 
which he “ can separate from others without the aid of a powerful 
magnifier and a vivid imagination.” 
A careful and earnest student from Kansas writes as follows: “I 
have lately collected a large number of Planorbis trivolvis from the 
rivers and creeks in this vicinity, and I find it a most interesting 
shell. I can take Binney’s Land and Fresh-water shells of North 
America and a box of these and duplicate a half dozen species figured 
and described in it.” And I believe the same will be found to be 
true of our Succineas which need a thorough pruning down in the 
matter of names. , 
And what is a variety? If species, as they are now recognized 
among conchologists, hopelessly run together, where shall the varieties 
appear? What is the difference between a variety and a species, is 
