* 



40 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXIV 



G. A-central very large; B and C centrals especially re- 

 duced : many marginals (100) with rather long blades; 

 R-central with rounded base; shell large, globose, that 

 of male with a sinus on outer lip; operculum with heavy 



calcareous plate Viana. Cuba. 



GG. All paired centrals more nearly uniform in size; few 

 marginals (28) with short, broad blades; shell de- 

 pressed, angular; operculum linear, with horny plate 



dominant Calybium. Indo-China. 



H. Shell with columellar folds, radula unknown 



Subgenus Calybium s. s. 

 HII. Shell without columellar folds; radula as above 



Subgenus Geotrochatella. 



Genus BOURCIERA Pfr. Ecuador. 



Bourciera Pfr. (1851). Type B. helicinaeformis Pfr. (1851). 

 Bourcieria auct., not of Bonaparte (1850), in birds. 



Pseudhelicina Sykes (1907). Proposed new name for Bourcieria auct.; not 

 Pfr. 



Bourciera, omitted from Wagner, has a paucispiral operculum. 

 Troschel (1856-63) describes and figures the radula of the type 

 species and remarks: "In regard to the structure of the radula, 

 the genus Bourciera belongs to the Rhipidoglossa, and indeed to 

 the family Helicinacea; in fact it agrees so with Helicina itself, 

 that a difference in the dentition can hardly be stated" (trans- 

 lation). His figure does not show definitely the structure of the 

 capituliform complex, which I regard as especially important in 

 the determination of relationships, but the centrals and marginals 

 appear quite similar to those of Hendersonia, and I believe the 

 i wo groups will be found to be quite closely related. There can 

 be no doubt of its position in the Helicinidae. 



Unless the structure of the operculum is secondary, this is pro- 

 bably the most primitive member of the family. As it is the only 

 genus confined to South America, and none of the other genera 

 appear to have developed very distinct groups on this continent, 

 it seems as if all of the South American Helicinidae are probably 

 quite recenl immigrants from the north and that Bourciera, like 

 the llama amongst the mammals, is a survival, in the Andes of 

 Ecuador, of a primitive type, which disappeared from its original 

 oearctic or holarctic home after its invasion of this new territory. 



This idea is further substantiated by the total absence of the 

 Helicinidae from Africa and the paucity and Oriental type of the 

 A.us1 mli.iii species. Probably it is safe to state that the Helicinidae 



