32 THE NAUTILUS. 



easily explained. That Say terms primary teeth what we now call 

 cardinals or pseudocardinals, may be mentioned by the way. 



As to the arrangement it is interesting to note that the first genus 

 is Helix (made up of our Polygyra, Zonitidse, Vallonia, Strobilops, 

 Patula [Pyramidula~\, Helicodiscus, variously mixed up); then fol- 

 low: Polygyrn (P. s. str.), Oligyra (= Helicma~), Planorbis, Lymnsea 

 (including Physcf), Succinea, 1 Cyclostoma (Valvata}, Ancylus, Palu- 



These things are mentioned just for an historical reminiscence, 

 and also to show the changes brought on by anatomical examination 

 and more minute distinction. 



Some notes on species : 



Helix lineata. Reference is made to Journ. Acad. Nat. Sc., I, 

 p. 18, but no mention of Planorbis parallelus. 



Succinea ovalis. Alt. 11.25, aperture alt. 8.75 mill. 2 Say states 

 that the species is common ; how is it, then, that no larger specimens 

 were found, if ovalis were identical with obliqua? and that Say de- 

 scribed the latter as new, only a few years later ? (as 17.5 mill, 

 high). A. Binney (Terr. Moll., II, p. 71) asserts that the two are 

 identical, or varieties of the same species, yet does not use the older 

 name ; and he does not state whether there are any undoubtedly 

 authentic ovalis Say on hand, giving evidence of the identity. In 

 the absence of such, doubts should be permitted. Dr. Dall seems to 

 have the same view. 



Unio crassus. From the description it is evident that not only 

 several species are included under the name as the author himself 

 suspects but that rather forms of Unio, resp. Quadrula are under- 

 stood, including undulata Barnes, 8 and probably tuberculata Raf. A 

 description of Lamps, ligamentina would be quite different, and es- 

 pecially so of the prevalent form of the Ohio river (= var. gibbus 

 Simpson). The figure has resemblance to a female L. liga- 



1 Yet he adds the remark : " The characters of the inhabitant (=soft parts) 

 are widely distinct from the animal of the Lymnsea, and are somewhat allied 

 to those of the inhabitants of the Helices." 



dina (our Amnicola, Pomatiopsis, Lioplax, Goniobasis, Vivipara, 

 Campeloma), Pupa, Polyphemus (= Glandina), the bivalves: Unio, 

 Alasmodonta, Anodonta, Cychrs, Cyrena. 



'Say gives the dimensions in inches; for convenience of comparing, they 

 are reduced to millimeters. 



3 As even more evident from the description of U. plicata, following. 



