27 



PLANORBIS PARVUS, Say. 



Plate 4.— Figs. 19—23. 



P. testa simplice, minima, tenui, Isevi, valde compressa; 

 supra in medio impressa; infra late et minime excavata: 

 anfractibus 4, rotundatis, utrinque pariter conspicuis: suturis 

 impressis. 



SYNONYMS AND REFERENCES. 



P. PARVUS, Say. Nich. Encyc, Am. ed., pi. 1, fig. 5. 



" " Gould. Invert, of Mass., p. 209, fig. 139. 

 P. ELE VATUS, Adams. Boston Journ. N. H., 3, pi. 3, fig. 15. 



" « Gould. Invert, of Mass., p. 207. 



LiSTEK, tab. 139, figs. 45—44? 

 "Favanne, pi. 63, fig. 3.— DiLLWYN."— Say, MS. 



DESCRIPTION. 



Animal brown, foot extending from the labrum 

 to the centre of the shell, rounded posteriorly, 

 sides parallel. 



Shell small, compressed, minutely striate, 

 smooth, flat above, with the centre impressed: 

 left side with a broad, shallow concavity: whirls 

 four, a great part of them, with the apex, visible 

 to the centre, on both sides: sutures equally 



