134 The Molluscan Family Planorbidae 



H . duryi intercalare 



Canal west of Boynton. Collected by W. F. Shay 



Santa Fe River, High Springs. Collected by T. van Hyning 

 H. duryi eudiscus 



Silver Springs, Marion County. Collected by T. van Hyning 



Geographical Distribution. As far as known, this group is found only 

 in the peninsuhi of Florida north to Bradford County. It is particularly 

 abundant in the Everglade region of southern Florida. 



Species Considered as Valid. Three species are recognized, one with 

 several races. 



Helisoma (Seyninolina) scalare (Jay) Hrlisoina (Seminolina) duryi intercalare 



Helisonia (Seminolina) duryi (Wethcrby) (Pilsbry) 



Helisoma (Seminolina) duryi seminole Helisoma (Seminolina) duryi eudiscus 



Pilsbry Pilsbry 



Helisoma (Seminolina) duryi normalc Helisoma (Seminolina) preglabratum 



Pilsbry (Marshall) 



For an extended account of the species of this subgenus see Pilsbry 

 1934, pp. 31-43. 



Geological Distribution. Pliocene to Recent fauna. 



Remarks. SeniinoUna is a characteristic group of Helisoma, differing 

 from typical Helisoma in the presence of a physoid shell, not only in one 

 distinct species, but in the variations of the races of another species. In 

 its anatomy, it differs from typical Helisoma in the rounded mesocone of 

 the lateral teeth wiiich are distinctly aculeate in Helisoma. The duct of 

 the penial gland is about twice as long as in Helisoma and the penial gland 

 is more elongated, narrower, and less cup-shaped than in Helisoma. 



Seminolina is a notable group of the subfamily Helisomatinae and one 

 of the most variable genera as regards species. The physoid aspect of its 

 type species, Paludina scalaris Jay, led the older conchologists to include 

 it in Physa and in the genus Ameria of the family Bulinidae. The largest 

 species, Helisoma duryi (Wetherby), is perhaps more variable than any 

 other species found in America, its extremes being from typical Physa- 

 shaped to flatly discoidal shell. The elongation of the spire always pro- 

 duces a physoid aspect. The races of duryi blend into each other and often 

 three forms will occur in the same lot, as normale, intercalare, and duryi. 



The Helisoma duryi complex includes several races more or less heavily 

 infested with parasitic worms. These include normale, intercalare, eudiscus, 

 and duryi. IVIany specimens were so badly infested that most of the organs, 

 especially the genitalia and liver, were completely obliterated. Helisoma 

 scalare was the least affected. 



Subgenus PIEROSO^IA Ball, 1905 

 Tjqie by original designation Planorbis trivolvis Say 



1865. Helisoma Binney (non Swainson), Land and FW. Sh. N. A., II, p. 112. No 



type cited. Includes mostly species belonging to Pierosoma 

 1872. Helisoma Tryon (non Swainson), Mon. Univ. FW. Moll. U. S., pp. 188, 198. 



Includes mostly species of Pierosoma. As subgenus 

 1883. Helisoma Fischer (non Swainson), Man. de Conch., p. 509. Type Planorbis 



trivolvis Say. As section of Planorbis 

 1899. Helisoma Martens (non Swainson), Biol. Cent. Amer. Moll., p. 381. Includes 



species now referred to Pierosoma 



