28 



pond in Door Park. Mj doscription is fullc^r tlian 

 tliat of Di-. Lea. 



Shell elliptical, of a cliestnut color, firiiKu- in t(\xturo 

 tlian P. r/i/rina, whirls live, spire obtusely elevated ; 

 aperture nearly two-thirds the length of the shell, and 

 compressed ; labrum sharp, with its inner mai'n-in i'(k1 ; 

 and further within the aperture, a chestnut colored 

 lin(; showing outside a whitish color ; l(»ngth 19 mill. 



Dr. Lea calls this the most remarkable Physa found 

 in this country. Tlu^ pond from which I obtained my 

 specimens, has the bad habit of getting dry eA^ery 

 season. The remarkable size of the shells as well as 

 their shape, at once attracted my notic-e. 'Piu^ species 

 disappear with the water, but for scn'eral successive 

 years, have reappeared with the advent of their natural 

 element ; or, the ova deposited have served to pi^rpet- 

 iiate the family. The above two species are all that I 

 can vouch f'oi- as living in this county. In the Lake 

 Michigan drainage aiound Chicago, PJiysa gyrina 

 attains a V(uy lai'ge size, but is ditferent in shape from 

 Physa Ilildrethiana. 



GENUS BULINUS, Adaxsox. 



SSI I.I.MJS HYI».>OKl n, Linn. 



Shell fragile, slender, polished ; whirls six, aperture 

 narrow, spire tapering, color light ja^Uowish, cohnnel- 

 lar fold slight ; length about 18 mill. Loc. stagnant 

 ponds near Illinois River. 



This species differs from Physa^ in being uiore 

 slender and mon; highly polished, and in having a 

 simple, unlVinged mantle. The slu^ll a])pears of a deep 

 black when the animal is within. 



