290 ALLOGNATHUS. 



Anatomy unknown. Distribution, southeastern China, Tonquin 

 and Cambodia. 



Among Old World Helices this peculiar group can only be com- 

 pared with the typical Helicodontas (pbvoluta, holoserica, diodouta, 

 etc.) of Europe and China. From these, Mollendorffia differs in the 

 fewer whorls, continuous peristome, etc. Still, I find no differences 

 of generic value in the shells; and, unless the anatomical features 

 prove peculiar, we can hardly accord the group higher rank than 

 subgeneric. In America, we find analogical shell structures in 

 Pleurodonte (Labyrinthus} leucodon and its allies, which somewhat 

 resemble H. trisinuata ; and H. horrida may be compared with 

 Epiphragmophora(Averellia) macneilli Crosse ; but these are merely 

 adventitious resemblances, due to the action of mechanical causes, 

 which have produced tridentism in many diverse groups of Helices, 



H. loxotatum Mab., vi, 13. H. erdmanii Schm. &Bttg. 



H. trisinuata Mart., vi, 1 1. Proc. Mai. Soc. Lond., i, pi. 9. 



v. sculptilis Moll., vi, 12. H. faberiana Moll., vi, 10. 



H. eastlakeana Moll., vi, 12. H. biscalpta Hde., vi. 9. 



H. hensaniensis Gredl., vi, 299. H. horrida Pfr., vi, 9. 



Genus ALLOGNATHUS Pilsbry, 1888. 



Allognathus PILS., Man. Conch. (2), iv, pp. 121, 149, type H. grat- 

 e&w;n. KOBELT Nachrbl. D. M. Ges., 1891, p. 140. Cf. SCHU- 

 BERTH, Archiv f. Naturg., Iviii, 1892, pp. 38, 61, pi. 4, f. 10, 11 (an- 

 atomy). 



Shell globose, thin, smooth, imperforate, with low spire of about 

 4$ whorls and obtuse apex ; last whorl descending in front, pale, 

 with five spotted bands. Aperture round-lunate, oblique ; lip ex- 

 panded, in the middle of the base closely appressed, the columellar 

 margin arcuate and rather wide. Type H. graellsiana Pfr., pi. 43, 

 figs. 39, 40. 



Jaw arcuate with a median projection, its surface entirely smooth. 



Radula very large (length 7, breadth 4 mill.). Teeth all of the 

 same form, strap-shaped, bent in a half circle, the cusp single, simple 

 and blunt (pi. 36, fig. 2, teeth from above, fig. 3, profile of cusps). 

 Outer teeth similar but somewhat smaller. 



Genital system resembling that of Helix but the sacculated 

 uterus extends far downward; the spermatheca duct is swollen 



