THE NAUTILUS. 59 



unmistakably adult, and that would be identified by anyone 

 as Lithasia (Angitrema) armigera Say, 1821. Two specimens 

 taken corresponded to what I have found recognized as 

 Lithasia (Angitrema) venusta Lea, 1841. At Kingston 

 Springs, Cheatham co., near the mouth of the river, armigera 

 was collected in numbers. In addition was collected plenti- 

 fully a Lithasia identical in shell characters with fuliginosa 

 of the Duck river. A few only show the link with geniculata. 

 A curious thing was the fact that all of these shells of the 

 fuliginosa form, when banded, had the banding formula not 

 of geniculata- fuliginosa^ but of Lithasia obovata Say. 



It is perhaps useful here to explain that though any given 

 species of the Pleuroceridae may have several banding ar- 

 rangements, yet in this given species will be found one for- 

 mula which occurs many more times than any other, constitu- 

 ting a characteristic the perplexed student of this family 

 feels he can be depend upon. Whether the Kingston Springs 

 shells show a relationship between geniculata through fuligi- 

 nosa, to obovata, or blow r this rule about banding formulas out 

 of water, is for some one more competent than myself to decide. 



On the findings of Dr. Ortmanu, fuliginosa cannot be recog- 

 nized as more important than a variety of geniculata. Under 

 Lithasia armigera might be listed these subspecies : 



Duttoniana (Lea), nearly smooth, or smooth, and having a 

 prolonged basal sinus. 



Angulata (Weth.), nearly smooth, or smooth, and lacking 

 the prolonged sinus. 



Parva (Weth.), a dwarf form, seemingly occurring with, 

 angulata. 



Venusta (Lea). 



Dowmei Lea, 1881, possibly only a mutation of armigera,. 



The genus Angitrema, with chief character " shell spin- 

 ous ", was established by Haldeman in 1841, the type to be 

 Melania armigera Say. Dr. Pilsbry x reduced it to the 

 position of a section under Lithasia. Even that leaves geni- 

 culata and armigera separated from some of their offspring. 

 There seems to me to be no other course now than to eject 

 Angitrema altogether. 



i.Froc. Acad. Nat. Sciences, 1896, p. 496. 



