1922] NATURAL SCIENCES OF PHILADELPHIA. 43 



certainly demands it generic recognition. It seems that Hendersonia 

 is a primitive genus which once had a wide holarctic distribution, 

 but which only survives in a few localities in Asia and North 

 America. The case of the giant salamander amongst the amphibians 

 (Ohio River, U. S.; and Japan) appears to be analogous. In this 

 connection the genus Dawsonella Bradley (1872), from the Car- 

 boniferous of Indiana, is at least interesting. If it actually belongs 

 in the Helicinidae, the circular aperture would seem to indicate 

 that it probably possessed a spiral operculum. 



An additional reason for the position of Hendersonia as a primi- 

 tive group, was found in the study of the radula of Aphanoconia 

 (Sphaeroconia) verecunda (Gould) 3 . This radula (Plate V, fig. 23) 

 is also quite close to that of Hendersonia, but its divergence is 

 along different lines from that of Oligyra, and apparently denotes a 

 divergent line of evolution. The large number of cusps on the 

 peculiar paired centrals (Table II), the long comb-laterals with 

 numerous pointed cusps, the exceptionally long accessory plates 

 with somewhat reduced wings, and the very long and slender 

 marginals give an assemblage of characters that separate this 

 group from any American one that I have examined. H . verecunda 

 Gould (1859) is here chosen as the type of Sphaeroconia A. J. 

 Wagner (1909). Verecunda A. J. W. (1909) is an exact synonym. 



Pilsbry and Cooke (1908) have described the radulae of H. 

 baldwini, uberta, laciniosa, and rotelloidea from Hawaii, and figured 

 those first and third. From their studies, it appears that the radula 

 of Sturanya Wagner (1905) (Type H. laciniosa Mighels, 1845) is 

 very close to that of Sphaeroconia, but that the radula of Oro- 

 bophana Wagner, 1905 (type H. uberta Gould, 1847), as they point 

 out, is considerably different. 



Genus OLIGYRA Say. Tropical and Subtropical America. 



Subgenus OLIGYRA s. s. Same distribution. 



Section Oligyra s. s. United States; New Mexico, Bermudas etc. 



Olygyra Say (1818). Type (monotype) O. orbiculata Say (1818). Easte/n 



Fla., U. S. 

 Oligyra Say (1819). Emended form of preceding; emended by Say himself. 

 Orbiculata A. J. Wagner (1905). Type (by tautonomy) O. orbiculata Say 



(1818). 



3 1 dried specimen; A. N. S. P. no. 78852; collected at Ryukyu, by Y. Hirase 

 (1900). 



