340 THE CHICAGO ACADEMY OF SCIENCES. 



REMARKS: Reflexa is one of the commonest of the Lymnaeas in 

 certain localities ; it is very variable and is frequently confounded with 

 long-spired specimens of Galba elodes. The spire of reflexa is always 

 longer than the aperture, and may be twice as long. As a general rule, 

 reflexa has higher whorls in comparison with their width than in 

 elodes; the last two whorls are disproportionately larger and the pe- 

 nultimate whorl is usually large and has a "puffy" appearance (in 

 elodes they usually taper gradually and regularly to a point) ; the 

 whorls are also rounder, with deeper sutures. Moreover, reflexa is 

 very rarely malleated, while elodes usually shows traces of malleation 

 due to its wallowing habit. The aperture in reflexa is also more half- 

 moon-shaped and has a peculiar "twist." A close study of the shape 

 of the whorls will almost invariably separate reflexa from elodes. 

 Failure to note these points has caused some authors to assert that 

 reflexa runs into palustris (elodes), but a study of abundant material 

 does not bear out this statement ; young specimens of reflexa and elodes 

 resemble each other, the parallel between them being the same as be- 

 tween immature Polygyra thyroides and P. albolabris. Even half- 

 grown specimens of elodes can be distinguished from reflexa by the 

 shape of the body whorl, which in the latter species is more com- 

 pressed and flattened than in elodes. The majority of specimens of 

 reflexa examined have been usually constant in form. The inner lip 

 is sometimes raised so as to make the aperture continuous (pi. XXXV, 

 fig. 15), and the epidermis is sometimes heavily zebra-marked, both 

 spirally and longitudinally. The spire varies somewhat in height. 

 Very old individuals which have survived until the third season are 

 exceptionally large and the aperture is peculiarly oblique and reflexed. 

 (PL XXXV, fig. 8.) 



Say's types of reflexa (two specimens) are still preserved in the 

 Academy of Natural Sciences of Philadelphia (No. 58639). The shells 

 consist of 6^ whorls, which are rounded and not flat-sided as in Say's 

 figure published in Binney, but more like Say's figure in the American 

 Conchology. (See plate XXX, figures 30, 31.) Haldeman's plate 8 

 is typical of the majority of specimens referred to reflexa. Crystal- 

 ensis (plate XXXVI, figures 7-11) is the immature state of reflexa, 

 a fact recently demonstrated by an ecological study of certain summer- 

 dry ponds or "swales" in northern Illinois. Both forms may be found 

 associated together, the fully mature reflexa being a crystalensis of 

 the third year. This immature form resembles elodes, from which it 

 may be distinguished by its more tightly coiled upper whorls, its nar- 

 rower aperture and more cylindrical whorls. 



