1 28 HELIX-OXYCHONA. 



Section VIII. OXYCHONA Morch, 1852. 



Oxychona MORCH, Cat. Yoldi, p. 14 (1852). H. and A. Ad. 

 Genera Kec. Moll, ii, p. 194. PFEIFFER, Malak. Bl. xxiv, p. 8 

 (1877). PFEIFFER-CLESSIN, Noment. Hel. Viv., p. 198 (1878). 

 FISCHER, Manuel de Conchyliologie, p. 471 (sect. Helicogena). 

 (1885). TRYON, Structural and Systematic Conchology, iii, p. 36. 

 Geotrochus (in part) ALBERS, Die Heliceen, p. 114 (1850). 

 ALBERS-MARTENS, Die Heliceen, ed. 2, p. 167 (1860). CROSSE ET 

 FISCHER, Moll. Mex. et 1'Amer. Cent., i, p. 291. WOODWARD, 

 Manual of Moll. p. 162 (1854). Leptoloma (in part) ALBERS- 

 MARTENS, Die Heliceen, p. 167 (I860). PFEIFFER-CLESSIN (in 

 part) Noment, Hel. Viv., p. 159 (1878X Corusia (in part) CROSSE 

 ET FISCHER, Moll. Mex. et dans PAmer. Cent., i, p. 296. Axina H. 

 AND A. AD., Genera Rec. Moll., ii, p. 193 (in part). Eurycratera 

 (in part) PFEIFFER-CLESSIN, Noment. Hel. Viv., p. 169. 



The section Oxychona as here defined, consists of an assemblage 

 of trochoidal Helices inhabiting the mainland of America from 

 Brazil to central Mexico. There is considerable diversity in respect 

 to carination and degree of depression of the spire, just as we find 

 in nearly all groups of Helices (conf. Strobila labyrinthica and S. 

 hubbardi ; Iberus muralis and I. sicana ; Stenotrema spinosa and S. 

 hirsuta, etc.). These differences have caused the species to be dis- 

 tributed by all authors who have heretofore treated of them into 

 numerous exotic groups to which they bear some resemblance. In 

 the Australo-oceanic group Geotrochus we have shells extremely 

 similar to Oxychona, and exactly paralleling in the variations in 

 form of its several species the series of forms presented by Oxychona. 

 Thus Geotrochus opalina Sowb. is like Oxychona pileiformis Mor. ; 

 G. strabo Brazier is like O. bifasciata Burrow ; G. ambrosia Cox, 

 flexilabris Pfr., ramsdeni Angas and many others are very similar 

 to O. trigonostoma Pfr. ; while the counterpart of O. guillarmodi 

 Shutt. is seen in numerous species of Chlorcea and Corasia. 



The anatomy is unknown. The shell is rather thin, whitish, with 

 darker spiral bands ; the surface is smooth, microscopically spirally 

 striate or granulate ; the aperture is like that of Caracolus in lack- 

 ing teeth. The species are forest-dwellers according to Albers and 

 Morelet. 



