96 AURIS. 



Gonyostomus BECK (in part), Index Moll., p. 53, for gonyostoma 

 (Fer.) Sowb., coneolor Bk., centiquadrus Val., multicolor (Rang) 

 King. GRAY, List, etc., P. Z. S., 1847, p. 174 (type gonyostoma). 



Stenostoma SPIX (in part), Test. Bras., 1827, not of Latr., 1810, 

 norofWagl., 1826. 



Anthinus ALB., Die Hel., 1850, p. 149; ALB.-MART., p. 189, 

 type B. multicolor. 



Pelecy chilus Gldg., ALB.- MART., Die Hel., p. 188, not Pleko- 

 cheilus Gtiilding, 1828, see this volume, pp. 62, 64. 



For anatomy see SEMPER, Reisen in Arch. Phil., Landmoll., pp. 

 151, 155 (bilabiatus, egregius, distort us). BINNEY, Ann. N. Y. 

 Acad. Sci., iii, p. 114 (glaber, multicolor, egregius'). 



Shell ovate, oblong, or fusiform, Bulirnoid or Auricula-shaped, 

 solid, of opaque, earthy texture and usually light color; rimate, 

 perforate or umbilicate; always sculptured. Aperture about half 

 the length of the shell, varying from ovate to ear-shaped and con- 

 torted, often notched or angular at base ; outer lip reflexed, evenly 

 arcuate or sinuous, often with a flange along its inner edge ; colum- 

 ella with a strong or weak entering fold. Nepionic shell very small. 



Mantle-edge with a long left body-lobe, or a small right and 

 divided left lobe. Kidney short. Genital system without accessory 

 organs, the spermatheca duct long, flagellum wanting (? or rarely 

 present). Jaw plaited, the plaits few or many, and either almost 

 completely soldered together and appearing merely striate, or less 

 united and as in Plekocheilus. 'Dentition as in Plekocheilus, and 

 showing the same variation. 



Type A. melastomus (Swains.) Spix. 



Ground snails, as far as known, ranging from Venezuela and 

 Trinidad to southeastern Brazil, nearly all characterized by con- 

 spicuously earthy texture and peculiar modification of the aperture. 



The genus is most nearly allied to Plekocheilus, the two groups 

 being separated upon shell characters alone, the anatomy, so far as 

 present information goes, affording no diagnostic differences. The 

 conchological divergence, however, is so great between the two 

 groups, that a union of them would seem a radical and uncalled-for 

 measure; while their separation as distinct genera is obviously an 

 aid to clear conceptions of the mutual relationships of the species 

 involved. 



