1920.1 NATURAL SCIENCES OF PHILADELPHIA. 195 



MOLLUSCA FROM CENTRAL AMERICA AND MEXICO. 

 BY HENRY A. PILSBRY. 



The following descriptions and notes are in continuation of those 

 published in these Proceedings for 1919, pp. 212-223. 



Further comparisons have shown that Donax mediamericana (op. 

 cit. p. 222) is merely a form of D. striata. The differences depended 

 upon are inconstant. 



Scolodonta seteki new species. Fig. ]. 



The shell is discoidal, broadly umbilicate, almost flat above, 

 thin, Isabella colored, slightly translucent. The surface is glossy, 

 finely striate above, more weakly so below. There are six narrowly 

 coiled, slowly increasing, convex whorls, the last, at the aperture, 

 nearl}^ twice the width of the preceding, rounded at periphery and 



Fig. 1. — Scolodonta zeteki. 



base, not descending in front. The umbilicus is conic, showing 

 all of the whorls. The aperture is slightly oblique, lunate, higher 

 than wide. Peristome thin and simple, the wddely separated ter- 

 minations joined by a very thin callus. 



Alt. 4, diam. 10.9 mm.; 6 whorls. Gatun. 



Alt. 3.4, diam. 9.1 mm.; 5.5 whorls. Gamboa. 



Canal Zone: Gatun (D. E. Harrower); Gamboa (James Zetek). 



Type No. 114,079, A. N. S. P. 



Readily recognized by its discoidal form. There is a very closely 

 related species in the collection from Venezuela without definite 

 locality (R. Swift coll.; No. 23,775), whitish, with the whorls a trifle 

 less closelv coiled. 



