GASTROCOPTA, AFRICA. 119 



The extreme similarity of some African and Mascarene 

 species to those of the Antilles naturally suggests that they 

 may be the slightly changed descendants of Antillean speci- 

 mens, imported on plants or otherwise by commerce, as species 

 of Opeas and Siibulina have certainly been spread. But there 

 are facts which cause me to hesitate before accepting the 

 hypothesis of recent introduction. We must consider the 

 occurrence of such forms in the most out-of-the-way places; 

 the wide distribution in Africa of G. damarica, in the Cape 

 Verdes of G. acarus. We may have here a case of parallel 

 modifications of very old and slowly changing forms. More- 

 over, each species is to be considered separately. Some local- 

 ities are more likely to receive importations than others. 



Species of Continental Africa and the Cape Verdes. 



Subgenus SINALBINULA (see pages 11, 103). 

 65 GASTROCOPTA PLEIMESI (Jickeli). PL 22, figs. 5, 6. 



Shell narrowly rimate, cylindric oval, whitish, diaphanous, 

 glossy, under a lens longitudinally irregularly substriate, cov- 

 ered with dirt. Spire slowly tapering, the apex obtuse. 

 Whorls 5, convex, regularly increasing, the last one-third the 

 length, 3-pitted, subcompressed basally, the neck rather 

 rounded, suture deep, slightly oblique. Aperture subcircular, 

 7-folded : two parietal folds, the right one almost bipartite by 

 a deep sinus (the anterior part smaller, acuminate, the back 

 part larger), the left one forming a minute denticle; two 

 columellar folds, the lower one in the angle of columellar and 

 basal margins. Three parietal plicaa, the upper punctiform, 

 middle one larger, the third longest. Peristome a little ex- 

 panded, sublabiate, white, the margins joined by a thin, line- 

 like callous. Length 2%, diam. 1, aperture alt. %, width % 

 mm. (Jickeli). 



Abyssinia: Habab Mts., Nakfa, in the gorge of Asqaq, 

 5664 ft. elevation, on bits of wood under rotten leaves and 

 stony talus (Jickeli). 



Pupa pleimesi JICK., Malak. BL, 1873, p. 106 ; Nova Acta, 

 vol. 37, p. 117, pi. 5, f. 9. 



