FAMILY LIMNIAD^E — PLANORBIS. 



65 



Planorbis elevatus. 

 P. id. 



Planorbis elevatus. 



Adams. Joum, Nat. Hist. Vol. 3, pi. 3, fig. 15 

 Gocld, Invertebrata of Mass. p. 207. 



Description. Shell small, faintly marked with incremental lines. Whorls three and a half 

 to four ; the tube not rapidly enlarging, and considerably flattened. Whole shell flat or 

 slightly elevated above, the tip depressed so as to form a small pit ; below with a deep fun- 

 nel-shaped cavity, the whorls appearing obscurely angulated : suture deeply impressed. Aper- 

 ture slightly oblique : its upper edge on a level with the spire, or slightly declining ; lower 

 edge descending considerably beneath the level of the under surface ; portion of the pre- 

 ceding whorl embraced by the aperture, constituting about one fifth of its circuit. 



Color. Light grass-green, translucent. 



Diameter, 0-25. Height, 0*1. 



Allied to parvus, which is, however, more depressed, aperture more oblique, and the upper 

 surface more broadly and deeply concave ; to hirsutus, which is more elevated, and deeply 

 concave above and below. Dr. Gould imagines that it will prove to be the immature shell of 

 some other species. 



Planorbis deflecttts. 

 P. id. 



Planorbis deflectus. 



Say, Long's Exped. St. Peter's, Vol. 2, p. 261, pi. 15, fig. 8. 

 Goold, Invertebrata of Massachusetts, p. 307, fig. 136. 



Description. Shell small, distorted, depressed, finely wrinkled : right side in general con- 

 vex, but with the centre slightly indented ; suture distinct; left or under side concave, forming 

 an expanded umbilicus, exhibiting one-half of each whorl. Whorls four or five, very much 

 depressed, descending to an acute lateral edge below the middle ; the last whorl turns some- 

 what suddenly downwards. Aperture large, ovate. Lip commencing below the keel, and 

 embracing but a very small part of the preceding whorl, much narrower from side to side, 

 and its plane oblique to the axis of the shell : lip simple, very slightly everted beneath. 



Color. Light greenish yellow or soiled waxen. Animal dusky above, with a dusky line to 

 the top of the tentacles. 



Diameter, • 4. Height, • 1 . 



Adhering to stones, etc. in ponds ; occasionally with scattering hairs on its surface. In 

 the very young animal, the remarkable deflection of the last whorl not conspicuous. 



Fauna — Part 6. 



