22 TRANSACTIONS OF THE WAGNER FREE 



Ameria scalaris (Jay) Dall. 

 Paludina scalaris ]a.y , Cat., 3d Ed., p. 112, plate i. figures 8, 9, 1S39. 

 Physa scalaris KaXAe^man, Mon. Limn., p. 34, plate iv. figure 9, 1S42. 

 Ameria scalaris Dall, Ann. Lye. N. H. N. Y., ix. p. 356, 1870. 

 Physa {Thomsonia) carijiifera Ancey, Le Naturaliste, Paris, 188S. 

 Helisoma scalaris Pilsbry, Conch. E.xch., IL p. 113, 1888 ; IH. pp. 41, 43, 1889. 



Caloosahatchie beds, rare ; Dall. Post-Pliocene of St. John's River, 

 Florida, common ; living in South Florida, not uncommon in small ponds and 

 rivulets at midsummer. 



Isidora is 2l Planovbis v^Wh elevated spire; it maybe either sinistral or dex- 

 tral, smooth or sculptured. For the forms with carinated whorls and sinistral 

 shells Adams proposed the subgenus Ameria. Whether the Floridian shell 

 is strictly pertinent to this group can only be finally decided when the form of 

 the tentacles and the dentition are fully known. At all events, it has nothing 

 in common with Physa except its sinistrorsity. I have never been able to ob- 

 tain a description of the animal or alcoholic specimens with the soft parts, and 

 would be greatly indebted to any correspondent who would assist me to ob- 

 tain them. 



The genus Isidora has been referred to Bulinus Adanson as a synonym, 

 but as Adanson was not a binomial writer, his name cannot be sustained against 

 one properly proposed. Adanson's shell was not congeneric with Physa 

 hypJioruin and other shells commonly referred to Bidinus. 



Family PHYSID/E. 



Since my establishment of this family twenty years ago, by pointing out 

 its anatomical characters and especially its remarkable dentition, it has been 

 universally adopted by writers on the subject. It is impracticable to distinguish 

 between the species with an entire mantle-edge and those which have it fringed, 

 when we possess only fossil specimens. 



Genus PHYSA Draparnaud. 



Physa Meigsii n. &. 



Plate 10, figure 12. 



Shell large, with six or seven polished whorls ; spire acute, whorls flattish 



and appressed, the suture somewhat irregular, but closely appressed in all 



cases ; length of spire to that of the last whorl as 5.5 to 40; surface of the 



whorls brilliantly polished, when perfect ; on the last whorl the incremental 



lines are somewhat fasciculated at the suture and indicate obscure waves 



across the whorl, beside which the surface is covered, except on the periphery, 



with microscopic, close-set silky strise ; near the suture on the last whorl and 



on all of the spires, in specimens with the surface perfectly preserved, by 



means of a good glass a fine, uniform waving of these strise is observable 



which gives a very elegant shagreened effect to the surface, different from that 



