242 AMERICAN JOURNAL 



Gmel., which (a little later than'iH". rufa) was also detected in 

 the canal. In two years the number of specimens became quite 

 considerable, since which time but few have been observed. 

 This species has also found its way into the Mohawk River, 

 where, however, only an occasional solitary specimen may be dis- 

 covered among the hundreds of specimens of other " Melanise " 

 that may come into the hands of the collector. 



Later another stranger comes to notice — Somatogyrus (An- 

 culosa) isogonus, Say. As in the two preceding instances but 

 few specimens were obtained. The character which this species 

 has among collectors as a "rare species" was apparent for two 

 or three years, after which it multiplied to an excessive extent, 

 so that in 1867 in some portions of the canal it was numerically 

 the most abundant species to be found. In 1868 its numbers 

 are largely diminished, no doubt by the severe cold of the winter 

 of 1867-8. This species has also become colonized in the Mo- 

 hawk River, where it fully sustains its reputation as a rare species, 

 as* scarcely two dozen specimens in all have been taken from the 

 river. 



In the spring of 1867, while the water was withdrawn from 

 the canal, opportunity was offered for exploring portions of its 

 bed not usually accessible. One portion of the canal of greater 

 depth than the main channel yet retained from two to four feet 

 of water. In this deep water were found a very limited number 

 of specimens of a slender, acute Amnicola, which has since 

 then been referred to Amnicola [Pal.) lustrica, Say. At no 

 previous time have any specimens comparable with those of the 

 spring of 1867 been found in this vicinity. In the spring of 

 1868 none were to be obtained from the locality that produced 

 them in 1867 — it being presumed that this species suffered as 

 did Somatogyrus isogonus by the severe cold of the winter of 

 1867-8. 



In November and December of 1864, by the side of a shaded 

 ditch near the Mohawk River, were found immense numbers of 

 a species of Vitrina. The specimens were very fine and attained 

 an average size of nearly ^ inch in diameter, many of the larger 

 ones exceeding somewhat this diameter. Since that time no 

 living specimens of Vitrina have been seen in this vicinity. It 

 may also be remarked that previous to 1864 the station which 

 produced the Vitrina had been visited yearly for small Helices, 

 but no specimens of Vitrina had until 1864 been detected, and 

 at that time only in that one limited station. 



The species which have been referred to above were unques- 

 tionably introduced. Melantho rufa is found both east and west 

 of the locality referred to, and it would be difficult to surmise 



