1897.] NATURAL SCIENCES OF PHILADELPHIA. 477 



NEW BRAZILIAN STREPTAXIDJE. 

 BY HENRY A. PILSBRY. 



In the course of identifying Brazilian Streptaxidce some time ago, 

 my attention was called to the fact that in the collection of the Acad- 

 emy there were several different and very distinct species labelled 

 " Streptaxis candidus Spix," mainly in the " Robert Swift " and "A. 

 D. Brown " collections. I was thus induced to reexamine the large 

 species of the group Artemon, to which these forms belong, and to 

 investigate their characters and literature. 



Tryon 1 enumerates the following species: S. candidus Spix (in- 

 cluding S. Spixianus Pfr.), S. intermedins Alb., S. regius Lobbecke, 

 S. wagneri Pfr., S. Rollandi Bern., S. Paivanus, conoideus, costulosus 

 and cypsele Pfr., S. apertus and depressus Martens. 



S. regius, Rollandi and cypsele I have not seen. The identity of 

 ■S. candidus Spix with S. Spixianus Pfr. is very uncertain. There is 

 nothing in the collection of the Academy altogether fulfilling the 

 requirements of the Spix-Wagner description, which indicates a 

 broadly umbilicated shell, of 25 mm. diam. and half that height. 

 The larger size of Pfeiffer's shell is of course not significant, for most 

 of these species periodically form expanded lips, which, with further 

 growth, remain visible, varix-like, on the base of the shell; so that 

 the size of apparently mature examples is not a safe specific crite- 

 rion. 



The following forms seem to be new : — 



S. helios n. sp. 



Shell depressed, with low-conoid spire, umbilicate, the umbilicus 

 deep and somewhat funnel-shaped, one-fifth the diameter of shell ; 

 rather thin and not very stixmg, buff tinted ; the surface with varn- 

 ish-like gloss, very smooth, with only a faint puckering below the 

 suture representing the costulation of the allied species. Apex 

 minute, smooth ; whorls fully 6£, moderately convex, at first slowly, 

 theu more rapidly increasing, the last decidedly wider than the 

 penultimate (viewed from above), well rounded at the periphery, 

 convex beneath, very obtusely subangular around the umbilicus. 



J Manual of Conchology, (2), I, pp. 61-63. 



