129 



testSB adequans ; columella modice plicata, valde callosa ; fauci- 

 bus luteo-rufescentibus. Long, f ; lat. ^ poll. 



Found by Dr. T. H. Webb, in the River Gila, and near San 

 Diego. 



Quite remarkable, as being the only species yet known which 

 has variegated coloration. The stripes are found on some part 

 of every shell, and many are prettily ornamented throughout. 

 In size and proportions, it may be compared with P. microstoma, 

 Haldeman. 



Planorbis ammon. Testa magna, discoidea, subconica, sub- 

 tiliter striata ; latere sinistro late et profunde concavo, anfractus 

 quaiuor obtuse carinatos exhibente ; latere dextro concavo, anfr. 

 duos cum dimidio rotundatos monstrante : apertura ovato-trian- 

 gularis, interdum utroque valde expansa : axis | ad 1 poll.; 

 diam. :^ ad ^ poll. 



Found by Dr. T. H. Webb, in the Cienaga Grande, or Colo- 

 rado Low Desert, and also by Mr. W. P. Blake. 



The specimens differ greatly in size, and in the development 

 of the aperture ; but all agree in the peculiar slope of the outer 

 volution, giving them a conical or dome-shaped form when lying 

 on the left side. Fully developed specimens are much like 

 P. corpulentus, Say, but the shape of the volution and aperture 

 differ, and the striae are less coarse, and more like P. glabraius, 

 Say. 



Planorbis gracilentus. Testa discoidea, compressa, albida, 

 concinne striata ; latere dextro planulato ; latere sinistro modice 

 concavo ; utrinque, anfrac. 4 rotundatis, anfr. externo ad periph- 

 eriam obtuse angulato: apertura perobliqua, rotundato-ovalis. 

 Axis I poll. ; diam. ^ poll. 



Found by Dr. T. H. Webb, in the great Colorado Desert low 

 lands. 



No North American species, of equal size, can be compared 

 whh this well marked, wheel-shaped species. Very small speci- 

 mens are like large specimens of P. deflectics, Say. A species 

 from the Nile is very similar. 



Amnicola protea. Testa, elongata, gracilis, variabilis ; anfr. 



PROCEEDINGS B. S. N. H, VOL. V. 9 MARCH, 18^5. 



