11 



The Nautilus. 



Vol. v. JANUARY, 1892. No. 9. 



ON SOME TYPES NEW TO THE FAUNA OF THE GALAPAGOS ISLANDS. 



BY WM. H. DALL. 



Dr. G. Bauer has recently made some energetic and praiseworthy 

 explorations in the Galapagos Islands, with the view of obtaining 

 material for a discussion of the origin of their fauna. Among 

 other things obtained was a series, small but extremely interesting, 

 of the land shells of the various islands of the group. This- collec- 

 tion in all probability is not exhaustive, but it seems by far more 

 complete than any yet made at tliis point and a full report upon it 

 is in preparation by the writer. Among the mollusks, which com- 

 prise a large number of races of Bulimulus (of the sections Pleuro- 

 pyrgiis, Nesiotus, Raphiellus, etc.) and Succinea (S. Bettii E. A. S.) 

 are four minute forms each of which introduces a wholly new arroup 

 to the faunal list of Galapagos land shells. Preliminary descriptions 

 of three are appended ; the fourth is a Pupa of the usual Antillean 

 type. 



Helicina (Idesa) nesiotica n. s. 



Shell small, depressed, four-whorled, with periphery rounded, base 

 moderately arched, and peristome not thickened nor reflected ; q\)\- 

 dermis of a bright reddish-chestnut, polished, but with very evident 

 and regular incremental lines, base with a thin white callus merg- 

 ing into the lower lip without notch or angle ; spire depressed, 

 suture very distinct, not channelled ; operculum smooth, whitish, 

 angulated only at the upper extreme; alt. of shell 2-3, max. diam. 

 3.3 mm. 



