390 TH E CHICAGO ACADEMY OF SCIENCES. 



These shells are very smooth, not malleated and some specimens are 

 short and resemble catascopium, though lacking the tumid whorls 

 and wide aperture. These small shells connect perfectly with the large 

 forms which are undoubtedly palustris. Such sets of shells have un- 

 doubtedly been the cause of the statement made by some concholo- 

 gists, that catascopium is only a form of palustris. Specimens of 

 catascopium from the Erie Canal and the Genesee River, Rochester, 

 New York, also somewhat resemble palustris in being thin-shelled 

 and somewhat elongated. It has been suggested (Crandall and others) 

 that perhaps these shells are hybrids, which fact might account for 

 Dr. Lewis' belief. 



Catascopium shows very beautifully the effect of environment on 

 the shell; as found in the lower Genesee River, Rochester, N. Y., 

 where the water is more or less quiet along the shore, the shells are 

 quite thin, and exhibit a large amount of variation in the comparative 

 length of the spire, the very short spired forms showing a tendency to 

 approach the pinguis-like aspect. The spire varies from one-half the 

 length of the aperture to more than equal its length. (PL XL, figs. 

 6-10). The catascopium of Pine Lake, near > Charlevoix, Michigan, 

 are very solid and heavy, and vary in the length of the spire to even 

 a more marked degree than do the Rochester specimens. (See plate 

 XL, figures 16-22). 



Say's types of catascopium are still preserved in the Academy of 

 Natural Sciences of Philadelphia. They are similar to Haldeman's 

 figures, but the spire is not as acute as the figures of Say (see plate 

 XXX, figures 25-26) would indicate. Binney's figure 80 is not typical 

 for the same reason. His figure 81 is better and fairly represents 

 the species. Say's pinguis was at first thought to be a distinguish- 

 able race of catascopium, but the examination of large series of speci- 

 mens from widely separated localities shows that no line can be drawn 

 between the long and short spired forms. Topotypes from near the 

 original locality are figured on plate XLI, figs. 2, 3, .which show the 

 variation in the height of the spire. Intermediate forms are plenti- 

 ful in the Delaware and clearly indicate the unity of the two forms. 

 Tryon's brownii is a small example intermediate between catascopium 

 and pinguis. Of the two type specimens, one is caperata and the 

 other is brownii, apparently not mature as there are but 4y 2 whorls. 

 An examination of certain specimens from the St. Lawrence River 

 listed by Dr. Whiteaves as solida (=apicina) reveals the fact that they 

 are short spired forms of catascopium. These specimens were first 

 cited by Bell, who was followed by Whiteaves and others. Some of 



