9 
32 THE NAUTILUS. 
undulatus, pustulosus, ete. In U. gibbosus the sexes may be rec- 
ognized with a fair degree of probability by the more inflated shells 
of the females. 
A decided difference we find in U. verrucosus Raf. (tuberculatus: 
Barn.), where the older females are considerably elongated at the 
posterior end, that part of the shell being rather even, without the 
characteristic undulations and warty prominences. In younger,. 
though fecund specimens, that feature is yet little marked. 
U. phaseolus shows no constant differences in the sutural shape of 
the shell, but a decided one on the inner surface, in older speci- 
mens. The female has, in each valve, a deep, oblique sulcus corre- 
sponding with and leaving room for the gravid outer branchie. 
In the female Marg. marginata the posterior end is directed 
downward and more inflated (with a stronger umbonal ridge), and 
the same can be said of “ An.” edentula, although it is less marked. 
6. Numerical proportion of Sexes.—In most species, the number of 
males is in excess over that of the females, often considerably. A 
few examples may be cited. Of 50 specimens of L. subrostratus 
Say, from a lake in Indiana, only about one-third were females, and 
the same must be said of a lot of Z. nasutus from Ohio. Here, as 
in many species, the females were averaging considerably smaller. 
Of 115 U. pyramidatus, from the Ohio River, 71 were males, and 
of eight retusus, seven were males, the eighth was young with the 
gonad undeveloped. It is a question whether this be the normal 
condition or due to local causes, or an evidence of beginning de- 
generation. 
In concluding, it may be said that the time has come when new 
species should be based not only upon the shells, but also the 
soft parts, if such be obtainable. 
New Philadelphia, Ohio, April, 1898. 
A NEW UNIO. 
BY BERLIN H. WRIGHT. 
Unio villosus sp. noy. 
Shell ovate-elliptical, somewhat inflated, smooth, very inequi- 
lateral, bluntly rounded or subbiangular behind, subtruncate before, 
umbonal slope uniformly rounded above, disappearing at the lower 
margin. Substance of the shell moderately thin; very slightly 
