128 HELIX-OXYCHONA. 



Section VIII. OXYCHONA Morch, 1852. 



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

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

 (1877). PFEIFFER-CLESSIN, Nornent. Hel. Yiv., p. 198 (1878). 

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

 (188o). 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 (1860). PFEIFFER-LESSIN (in 

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

 ET FISCHER, Moll. Mex. et dans 1'Amer. 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 1 the mainland of America from 



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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 (cow/. Strobila labyrinthica and S. 

 hubbardi ; Iberus mural is and I. sicana ; Stenotrema spinosa and S. 

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

 tributed bv all authors who have heretofore treated of them into 



mi 



numerous exotic groups to which they bear some resemblance. In 

 the Australo-oceanic group Geotrochus we have shells extremely 

 similar to Oxvchona, and exactlv paralleling in the variations in 



* t. A O 



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 An^as and many others are verv similar 



i/ */ 



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 apertuie is like that of Caracolus in lack- 

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

 Morelet. 



