170 



55. lecythoides, Benson. 



56. limosa, Say. 



57. lustrica, id. 



58. magnifies, Conrad. 



59. marginata, Michaud. 



60. rnelanostoma, Benson. 



61. miliaris, Parreys. 



62. multicarinata, CiarcW. 



63. Naticoides, Fe'russac. 



64. nigra, D'Orbigny. 



65. nucleus, Thompson. 



66. obesa, Philippi. 



67. obtusa, Troschel. 



68. olivacea, Sotcerby. 



69. Parchappii, B-'Orb. 



70. Parreyssii, Pfeiffer. 



71. parvula, Gailding. 



72. patula, Brumati. 



73. peristomata, If Orb. 



74. Petitiana, «?. 



75. petrosa, Gould. 



76. ponderosa, #«?/. 



77. piscium, D'Orbigny. 



78. porata, -Say. 



79. pulchella, Benson. 



80. pyramidata, Bnscli. 



81. radiata, Benson. 



82. Kemossii, w?. 



83. rubens, Menke. 



84. scalaris, Jay. 



85. similis, Michaud. 



86. semistriata, D'Orb. 



87. striata, it?. 



88. subcarinata, #«y. 



89. subpurpurea, i«?. 



90. Swainsoni, Morc/t. 



91. thermalis, Draparn. 



92. tricarinata, Anton. 



93. Troostiana, im. 



94. unicarinata, Sowerby. 



95. unicolor, Lamarck. 



96. viridis, m/. 



97. vivipara, i<#. 



98. Warreni, Shuttleworth. 



Figure. 



Paludina oxytropis. PI. 17. Tig. 93. Shell, a fine keeled species, 

 covered with a dark horny epidermis. 



Genus 3. VALVATA, Mutter. 



Animal ; toith a short disk, bilobed or forked in front. Head 

 with long slender tentacles, at the outer base of which are situ- 

 ated the eyes, sessile ; gill long, plumose, pectinated, partially 

 eocserted. 



Shell ; discoid or turbinated, umbilicated, rather thin ; whorls 

 symmetrically tubular, sometimes smooth, sometimes keeled or 

 striated ; aperture circular, with the margin continuous. 



In this genus is comprehended a small group of fresh-water mollusks, 

 living on aquatic plants or under stones, in gentle rivers, lakes, and ditches, 

 comparatively minute in size, and having a spiral cyclostomoid shell. Only 

 eleven species are known, and they are all inhabitants of the temperate and 

 north temperate regions of the globe, — chiefly in Europe, and in North 

 America. The animal, of a dusky-grey colour, is not much unlike that of 

 Paludina, except that its eyes are not raised on pedicles, and the shell, 

 without sculpture, is of the same sombre greenish hue, sometimes inclining 

 to yellow. 



