1896.] NATURAL SCIENCES OF PHILADELPHIA. 427 



quently the sectional name proposed for it must fall into the syn- 

 onymy of that given earlier to B. nux and its allies. It is probably 

 •due to the great rarity of this species that its situation in accepted 

 systems has not been challenged before this ; certainly if it had been 

 as common as B. nux, the facts could hardly have escaped attention 

 so long. I have not found anywhere any reasons stated for putting 

 the species into Buliminus rather than Bulimulus where it really 

 belongs. 



The name Omphalostyla was applied by Schliiter to Bulirni with 

 the pillar vertically twisted, and his sole example was the African 

 shell, since better known under the name Achatina ustulata (Lam.) 

 Menke. It was probably to some accidental confusion of the spe- 

 cies with the Bulimus ustulatus Sby. of the Galapagos, that is due 

 the application by the brothers Adams of Schliiter's name to the 

 Ncesioti. 



The type of the section Pelecostoma Reibisch, is a Ncesiotus which 

 shows a ridge at the base of the pillar which gives a peculiar chan- 

 nelled aspect to the adjacent part of the aperture. This feature will 

 be found more or less distinctly present in some specimens of almost 

 any Galapagos species of which a large number is examined, show- 

 ing that it is dynamic or individual, and not of systematic value. 

 The second species of this " section " is Leptinaria chathamensis, a 

 species belonging to a totally distinct group. The name Pelecostoma, 

 therefore, may be safely laid away on the synonymic shelf. 



The question remains as to whether the section Ncesiohis has any 

 just claims to be separated from Thaumastus, Scutalus and other 

 nominal sections of Bulimulus into which so many diverse forms 

 have been gathered. The diagnostic characters given by von Mar- 

 tens in his second edition of Albers are certainly not distinctive or 

 •even characteristic of the whole group, or even of several separate 

 species of the same group. The shells are by no means always 

 *' aperte perforata," even in the same species ; the columella is as 

 often " plicata " as " recta," and the peristome, while generally 

 "simplex," and sometimes ** acutum," is not seldom denticulate or 

 tuberculous and more or less distinctly reflected. The anatomical 

 details, as elsewhere shown, oflfer no characters by which the species 

 may be differentiated from many of the Bulimuli of the mainland. 

 The utmost that can be said, therefore, is that Ncesiotus is a con- 

 venient terra for the geographical group inhabiting the Galapagos 

 Islands, and, as such, we may retain it, without giving way to the 

 ■delusion that it stands for anything more important. 



