AMI'lIIBULIMIN^E. 211 



Sub-family AMPHIBULIMIN^E. 



Includes Amphibulima, Rltodonyx, Pdlicula, Gceotis, Peltella, 

 Simpulopsis and Eudioptus. 



Arboreal or sub-arboreal Bulimulidce with the shell degenerate as 

 a protective organ, Succinea-shaped, ffaliotis-shaped, or in the less 

 reduced forms, globose or ovate ; always thin, and mainly cuticular ; 

 unicolored and more or less translucent (except in Ampltibulima). 

 Jaw, radula and genitalia of Bulimulid type. 



An American group of genera, which agree in having the shell in 

 various stages of degeneration. In Bulimutopsis only the incipient 

 stage of this process of reduction has been reached ; Simpulopsis is a 

 later sta^e, and Peltella and Gceotis seem to be terminal members of 



O 7 



the series, being slug-like in form. Amphibulima with its satellite 

 groups Rltodonyx and Pellicula, stand a little apart from the other 

 series. The exact inter-relationships of the various genera cannot 

 be understood until a comparative study of the soft parts, more fund- 

 amental than has yet been made, is undertaken. Peltella is the only 

 genus which has been adequately investigated. It may turn out 

 that Drymceus, Liostraciis and Bulimulopsis converge to a common 

 origin ; Simpulopsis being a further development of the last of these 

 groups, and Peltella another member of the series. Just where 

 Platysuccinea belongs is doubtful, but Gaotis may be related to it as 

 Peltella to Simpulopsis. Amphibulima may trace its ancestry to the 

 Liostracus- Bulimulopsis root, or it may possibly be descended from 

 Bulimulus. I look to the general arrangement or " topography " of 

 the viscera, for the solution of these problems, rather than to any 

 information to be gained by study of the details of genitalia or teeth. 

 Our knowledge of the anatomy of the Ampkib idint ince is due 

 chiefly to Dr. Paul Fischer, Dr. H. von Ihering, and Mr. W. G. 

 Binney, all of whom have contributed valuable data. 



Key to genera, by shell-characters. 



I. Shell subglobose, ovate or oblong, varying in form from 



Naticoid to Bulimuloid. SIMPULOPSIS, p. 212. 



II. Shell depressed, the whorls open beneath, columella reduced 



to a spiral rib not concealing the interior of the whorls. 



PELTELLA, p. 231 ; G^OTIS, p. 227. 

 III. Shell Succinea-shaped. AMPHIBULIMA, p. 232. 



