34 



imperforate; spira breviuscula; suturis parvis; anfractibus quinis, subcon- 

 vexis; apertura subgrandi, ovata. JIab. Oahu. — Prof. Nuttall. 



Paludina regularis. Testa subglobosa; subcrassa, vindo-cornea, laavi, im- 

 perforate; spira brcvissima; suturis iinprcssis; anfractibus quinis, convexis; 

 apertura magna, ovata, intus caarulea. JIab. Ohio ? — T. G. Lea. 



Paludina obtusa. Testa subcylindracca, subtenui, tenebroso-viridi, lasvi, 

 minute perforata; spira brevi, ad apicem valde obtusa ; suturis impressis; an- 

 fractibus quaternis, convexis; apertura parva, subrotunda. Hah. Ohio. — Dr. 

 Kirtland. 



Paludina Troostiana. Testa ventricoso-conoidea, tenui, pellucida, luteo- 

 cornea, lrevi, perforata; spira brevi; suturis valde impressis; anfractibus qua- 

 ternis convexis; apertura magna, rotundata, alba. Hah. Tenn. — Dr.Troost. 



Jinculosa Troostiana. Testa ovato-conica, crassa, minute rugosa, tenebroso- 

 fusca ; spira subclevata ; suturis subimpressis; anfractibus planulatis; aper- 

 tura rotunda, intus casruleii; columella crassa, vel alba vel carnea. Hah. 

 Tenn. — Prof. Troost. 



Anculosa gibbosa. Testa subglobosa, gibbosa, crassa, subnigra, crebrestri- 

 ata; spira brevi; suturis impressis; anfractibus subplanulatis ; apertura sub- 

 quadrangulari, vel carnea vel albida. Hah. Tenn. — Prof. Troost. 



Anadosa dentata. Testa subglobosa, crassa, subnigra ; spira brevi, obtusa; 

 suturis impressis ; anfractibus convexis ; apertura magna, subrotunda ; colu- 

 mella crassa, dentata. Hah. Vicinity of Richmond, Va. — J. A. Warder, M.D. 



Anculosa carinata. Testa ovato-conoidea, carinata, tenebroso-olivacea; spira 

 breviuscula; suturis parvis; anfractibus senis; apertura parva, rotunda, intus 

 albida, sulcata; columella subcrassa, purpurea. Hah. Roanoke River, La- 

 fayette —J. A. Warder, M.D. 



Anculosa variabilis. Testa obtuso-conoideS,, crassa, vel fasciata vel cornea 

 vel carinata vel lsevi ; suturis linearibus; anfractibus senis, planulatis; aper- 

 tura magna, subrotunda; columella crassa, vel alba vel purpurea. Hah. 

 Roanoke River, Lafayette. — J. A. Warder, M.D. 



Amnicola orhiculata. Testa orbiculari, subtenui, luteola, lasvi, umbilicata; 

 spira brevi; suturis valde impressis; anfractibus quinis, inflatis; apertura 

 magna, rotunda. Hah. Springfield, Ohio, and Schuylkill ? near Philadel- 

 phia. — T. G. Lea. 



Amnicola parva. Testa obtuso-conica, subtenui, luteola, lasvi, umbilicata; 

 spira brevi; suturis impressis; anfractibus quaternis, inflatis; apertura magna, 

 subrotunda. Hah. Springfield, Ohio. — T. G. Lea. 



Jo tenebrosa. Testa fusiformi, subtenui, subnigra, lasvi ; spira conica ; su. 

 turis vix impressis; anfractibus senis, subplanulatis; apertura irregulariter 

 pyriformi, intus purpurea. Hub. Tennessee. — S. M. Edgar. 



Mr. Lea mentions, that regarding the sexual difference in 

 the family Nai'des as no longer a matter of doubt, his attention 

 had been given to the length of gestation and the periods of 

 parturition. With this view tables were made of a series of 

 observations, carried through nearly three consecutive years 

 by Mr. T. G. Lea, at Cincinnati. These prove that many spe- 

 cies in the same genus differ in their periods. In the course of 



