ODONTOSTOMUS. 39 



pericardium, triangular. Ureter and secondary ureter closed through- 

 out. 



The right ocular retractor passes between branches of genitalia. 



Distribution, eastern South America, Brazil below the Amazon to 

 northern Patagonia. 



A genus presenting great variation in form of the shell and de- 

 velopment of apertural teeth. Through the section Moricandia it 

 approaches Anctus ; through Plagiodontes, Tomigerus ; while there 

 are several species with simple apertures, by degeneration of the 

 teeth, which are difficult to separate from Bulimulus or Drymxus. 

 The apical sculpture in the typical subgenus is identical with that 

 of Drymdeus, while in the subgenus Spixia it resembles Orthotomium, 

 and in Hyperaulax and some Plagiodontes it is like that of typical 

 Bulimulus. Unlike those genera of Bulimulinse, we have transition 

 forms of apical sculpture in Odontostomus^ to some extent connecting 

 the several types. 



According to Jeffreys, there is an earlier name, Odontostoma 

 of Turton (1829), proposed as an emendation of Odostomia, but I 

 have been unable to find the paper cited by him, and no other author 

 or bibliographer seems to be aware of its existence. Under the cir- 

 cumstances it seems needless to dispute the validity of Beck's Odon- 

 tostomus, especially as the two names differ in gender, an invariable 

 element in generic nomenclature. Odontostoma and Odontostomus 

 have both been used for other groups later than the date of Beck. 



Gray selected " Hel. gargantula^ as the type of the genus Odon- 

 tostomus in 1847 (P. Z. S., p. 174), Beck's gargantula being the 

 odontostomus of Sowerby. But previous to this, in 1840, that species 

 had been made the type of Macrodontes, rendering Gray's selection, 

 unlawful. About the same time Herrmannsen, in the Indicts 

 Generum Malacozoorum Primordia, ii, p. 138, gave " Helix gargantua 

 Fer." as type of Odontostomus. This restricts that genus to the allies 

 of 0. pantagruelinus, which is identical with Ferussac's species. 



Subgenera and Sections of Odontostomus. 



I. Aperture without teeth or folds of any kind. 



a. Aperture angular or having a " spout " at the base. 



Sect. Moricandia, p. 40. 



a. 1 Aperture ovate, rounded below, species of sections Bahi- 

 emis, p. 46 ; Spixia, p. 66 ; Odontostomus, p. 62. 



