THE NAUTILUS. 55 



synonymy, and substituted his description of P. oleacea for that of 

 Lea. The species are widely different, and were so acknowledged 

 by him in later years. The form which I refer to this species may 

 be described as follows : 



Shell elliptical, thin, pellucid, smooth and generally shining, lines 

 of growlh scarcely perceptible, spire rather short and obtuse, sutures 

 impressed, aperture elliptical, axis straight, with varicose bands 

 when mature, and diameter from two-fifths to one-half the length. 

 The outline is almost exactly that of an elliptic spring. All the 

 varieties are small, not exceeding a half inch in length. 



Physa troostiana Lea is a more robust form, more obtuse, and the 

 diameter a little greater in proportion to the length. Its habitat is 

 along the Ohio valley. 



Physa elliptic a minor n. v. was sent to me from Grand Rapids, 

 Mich., by Mr. Streng. It is very small, being only four to five mm. 

 in length, rather cylindrical in form, whorls three, convex, sutures 

 impressed, spire slightly elevated, surface highly polished, color 

 deeper than the type. At first I thought they were immature, but 

 the lip has a well defined rib on the submargin, and I now think 

 they are a miniature form of this species. 



Physa deformis Currier probably belongs here, and may be a 

 variety, but for the present I prefer to consider it only a form. It 

 may be a larger form of P. elliptica minor ; if so it will take its place. 



Forms : P. aurea Lea, P. febigerii Lea, P. niclclinii Lea. 



This species is distributed sparingly over all the region east of the 

 Mississippi and north of Tennessee. 

 Physa niagarensis Lea. 



This species was described in 18G4 from forms taken in Niagara 

 river, N. Y., but has generally been considered a variety of P. 

 integer Hald. In fact I have held the same opinion until quite 

 recently. In the last few years I have had opportunity to examine 

 examples of P. integer from over fifty localities, about one-fourth of 

 which were properly referred to this species, and from these exami- 

 nations and the places from which they were taken, I feel satisfied 

 that this form is not a variety of P. integer. If it is not entitled to 

 rank as a species, it should be referred to P. helerostropha as a 

 variety. 



They vary but little, but the largest part of those I have examined 

 have the form of P. heterostropha, except that the spire is a little 



