140 OXYSTYLA, SOUTH AMERICAN. 



lete in places and on the base, on a dirty flesli-tinted ground, and no 

 dark varices, though of rude, frequently arrested growth. The lip, 

 parietal wall and apex are whitish. 



From the Rio Hacha, a series of eight specimens is before me, 

 some of which are figured, pi. 30, figs. 55, 56, 57. They vary from 

 the typical coloring to more heavily-marked forms, and through 

 specimens with fainter and fainter stripes, to a white form with no 

 stripes, a chestnut basal band, and traces of a peripheral band. The 

 intergradation is quite complete, and could be doubted by no one who 

 saw the shells. All of them are smaller than Maracaibo specimens, 

 an average one measuring, alt. 40, diam. 23, longest axis of aper- 

 ture 22 mill. 

 Form imitator n. PI. 30, figs. 49, 50, 51, 52, 53, 54. 



From near Maracaibo we have a series of shells (pi. 30, figs. 49, 

 50, 51, 52) which vary from (1) slightly yellowish-white, absolutely 

 bandless and with no stripes; varices none, or one narrow olive line; 

 aperture white or yellowish inside, the apex, lip and parietal wall 

 white, to (2) one to three banded with brown or purplish-brown on 

 a white or flesh-tinted ground, varices, lip and parietal wall dark, apex 

 dark or white, or (3) in addition to these markings, having extremely 

 faint gray or brown longitudinal undulating stripes, apex white (fig. 

 50). Measurements are as follows : 



Alt. 52, diam. 30^, longest axis of aperture 31 mill, (albino). 



Alt. 51, diam. 30, longest axis of aperture 29 mill. (3-banded). 



The young (pi. 30, fig. 52) look like 0. ferussaci tricincta, but 

 there is a fourth, (circum-columellar) band well developed. 



Exactly the same form occurs at Barranguilla (pi. 30, figs. 53, 54), 

 the columella in these being either rather straight and stout, and the 

 spire without markings, or the columella slighter and concave, spire 

 conspicuously banded ; varixed, and with a chestnut streak behind 

 the varix. 



Besides the localities mentioned above, this form has been collected 

 at Santa Marta, in Colombia, by Grosskopf : on the Magdalena river, 

 by Wallis, and in Ecuador at San Juan de la Costa, by Dr. Reiss. 

 It occurs almost everywhere with the striped typical form of the spe- 

 cies. Dr. von Martens reports it, under the name tricincta, from the 

 Maranon river, Peru. 



