NATURAL SCIENCES OF PHILADELPHIA. 593 



they can be traced to injuries inflicted on the margin of the mantle at an 

 earlier stage of existence, while rufa presents these characters as the indica- 

 tions of a variety. 



Reversed specimens among the embryonic young do not seem to be as 

 numerous as in decisa or Integra, though they are not rare. They seldom 

 survive separation from the parent. Of many hundreds of specimens taken 

 of all ages, only a single reversed specimen inch in diameter attests their 

 existence after exclusion. No distorted specimens, either young or adult, 

 have yet been detected. 



This species has within a few years been introduced at the points where 

 observed. It prefers to associate with Integra rather than with decisa, and 

 this leads to the supposition that it is carnivorous, though no evidence has 

 been found which is demonstrative of that fact. 



The writer has been favored with proof sheets of a Descriptive Catalogue of 

 the species of Amnicola, Vivipara, &c, of North America, by W. G. Binney. As 

 I do not hope to alter Mr. Binney's views by any sugestions made to him, 

 the following are offered for the consideration of those who might otherwise 

 accord too much to Mr. Binney's somewhat sweeping generalizations. 



It is quite probable that many small molluscs, which are at present placed 

 in genera to which they seem most nearly allied by the forms of their shells, 

 will hereafter be separated when their soft parts have been studied. Two 

 instances appear in the preceding papers "Amnicola isogona, Lea," and 



" (Cydost.) lapidaria, Say." Perhaps a third (Amnicola atteniiata, 



Hald., 3d page Des. Cat.) deserves consideration, under a future review of Am- 

 nicola. There are good reasons for believing that the forms of the shells of 

 the various species of Amnicola are embraced within limits typified by A. 

 tenuipes, Hald., and A. isoyona, Lea. A species more slender than A. tenuipes 

 should certainly have the evidence of the soft parts to confirm its position, 

 and it is unfortunately the case that these are too often passed over hurriedly 

 or entirely neglected. 



It is quite probable that " Amnicola proiea, Gould," will be found not to be 

 an Amnicola. 



Amnicola (Pal.) lustrica, Say, if Mr. Say's remarks on that species are en- 

 titled to any consideration, probably covers some such a shell as Valvata 

 pupoidea, Gould. 



Amnicola granum, Say. This species may perhaps be the same as Amnicola 

 obtusa, Lea. 



Specimens of this species (granum) found in near, but dissimilar, locations, 

 present great variations in magnitude and color. 



Mr. Binney's treatment of the several species of Paludina (Vivipara), the 

 apicial whorls of which are carinate, should be modified to conform to the 

 rules he applies to decisa and its analogous forms, or he should abandon the 

 position he has assumed with regard to decisa. It is quite as plain that Pal. 

 sttbcarinata, Say, should be made to embrace as varieties all the species with 

 carinate apicial whorls as that decisa should embrace so many species as Mr. 

 B. has assigned to it. 



On page 22 of Mr. Binney's paper is a figure of decisa, which may be regarded 

 as presenting a tolerable outline of the typical form of that species, as first 

 understood by Mr. Say. On page 23 is a figure of a deformed Pal. Integra, 

 the malformation resulting from an injury imparted to the margin of the 

 mantle of the animal in an earlier stage of growth. The original specimen 

 from which the figure was made is in the possession of the writer. 



Page 24, fig. 37, is a specimen of P. Integra, in which the whorls are drawn 

 to the axis. The parts which should be applied to the preceding whorls are 

 somewhat drawn away at the suture, and are eroded. 



Page 26, fig. 38, is correctly named Pal. (Vivi.) Integra. 



Page 32, fig. 38, a reversed shell. All our olivaceous species produce this 

 form, and it cannot be regarded as a normal species. 



1862.] 41 



