NATURAL SCIENCES OF PHILADELPHIA. 587 



Eemarks on some species of PALUDINA, AMNICOLA, VALYATA, and 



MELANIA. 



BY JAMES LEWIS, M. D., MOHAWK, N. Y. 



Amnicola (Pal.) limosa, Say. Soft parts. 



Foot seen below, truncate anteriorly, with acute angles laterally, the foot 

 being constricted. Back of the constriction the foot dilates to nearly or quite 

 the width of the anterior, the sides being parallel, thence posteriorly about 1\ 

 diameters of the foot ; posterior termination an abruptly-shortened wedge. 

 Colors variable. In some specimens there are longitudinal strips of flesh 

 color on the inferior surface of the foot, widest behind the constriction, and 

 growing narrower posteriorly. Between these strips is a wider area of slate 

 color, with a few faint granulations. In other specimens the foot is bordered 

 with white on each side, the flesh color of the preceding variety being replaced 

 with what appears to be a band of compact granulations, which become less 

 numerous posteriorly; a few are seen in the central portions of the foot, where 

 they appear to be embraced in the parenchyma of the foot. Other specimens 

 are observed in which the visible soft parts are of a very uniform salmon color 

 without any observable markings on the surface. In these the bands 

 which appear on the mantle of other specimens, visible through the shell, are 

 absent. 



No obvious markings have been detected on the superior surfaces of the foot 

 in any instances. A few specimens, however, in favorable light, present 

 slight markings on the superior lateral portions of the foot, too indistinct to have 

 a name. 



The rostrum seen below has a strongly-impressed central line, which ex- 

 tends over its anterior extremity. In most instances the superior surface of 

 the rostrum has a dark longitudinal strip extending from the head forward, 

 growing indistinct and becoming lost before the extremity is reached. Each 

 side of this dark strip is an interrupted and not very well defined line of light 

 colored or yellowish granulations. The lateral portions of the rostrum are 

 marked by a dark strip that becomes more dense and broader as it recedes 

 along the sides of the head beneath the tentacles. These strips are more varia- 

 ble than the central strip. 



The tentacles are directed obliquely forward and are nearly parallel. They 

 are not always equally developed, being sometimes malformed ; the malfor- 

 mations usually manifested are slight deviations from a right line, with con- 

 tractions in length. Either tentacle may be seen to be affected in this way, and 

 sometimes both. In a considerable number of specimens, the inferior surface 

 of the tentacle presents a well-defined black line extending from the base to 

 near the tip. This line is not always present in both tentacles, and seems to 

 be more frequently wanting in the right. It is sometimes irregularly inter- 

 rupted, and may be so in one or both tentacles. When interrupted, the ten- 

 tacle may also be seen to present other irregularities. The eye is obviously 

 inserted in the dilated base of the tentacle, and less obviously in the head at 

 the base of the tentacle. 



Neck of the animal large and robust ; superior lateral portions of the foot and 

 neck without fold or sinus . 



In younger specimens the general appearances are the same, except that the 

 foot presents rounded lateral and posterior outlines, and the foot is usually a 

 little smaller in proportion to the size of the shell. The movements of the 

 animal are quite brisk, and free from hesitation, and have the graceful, gliding 

 motion peculiar to the genus. 



Ammcola (Pal.) geana, Say. 

 Paludina lustrica, Ad. (Thompson's Vermont.) 



1802.] 



