18 HELIX PLAGIOPTYCHA. 



Alt. 6-7, diam. 12-13 mill. 



Hayti. 



H. loxodon PFR. Zeitschr.f. Mai. 1850, p. 73; and Conchyl. Cab. 

 t. 133, f. 7-9. REEVE, Conch. Icon., f. 268. 



More regularly and finely sculptured than H. albersiana, and gen- 

 erally with less elevated spire, and less expanded/ more reflexed, 

 basal margin to the peristome. There are two forms of aperture ; 

 one in which the ends of the peristome converge considerably, the 

 other with the basal margin nearly straight, almost closing the um- 

 bilicus by its expansion. 



H. BAHAMENSIS PfeifFer. Pi. 19, figs. 31-33. 



Narrowly umbilicate, depressed, thin, white, somewhat shining, 

 very finely obliquely striate ; spire low-conical, apex rather obtuse, 

 sutures impressed ; whorls 4-2-. moderately convex, the last sub- 

 depressed, descending anteriorly, slightly constricted behind the 

 aperture; aperture very oblique, oval-lunate; peristome simple above, 

 expanded below, terminations converging ; base with a strong trans- 

 verse callous tubercle inside, removed from the edge of the aperture, 

 its position marked outside by a wrinkled tract ; umbilicus partly 

 covered by the expansion of the lip; parietal callus very light. 



Alt. 6, diam. 10 mill. ; alt. 8, diam. 15 mill. 



Turk's Island, Bahamas. 



H. bahamemis PFR. P. Z. S. 1845, p. 66 ; Monogr. i, p. 383 ; Con- 

 chyl. Cab. p. 353, t. 41, f. 7-9. REEVE, Conch. Icon. f. 276. 



This form seems to me to differ from H. duclosiana in being more 

 elevated, less shining, more strongly striate. It is not so strongly 

 striate as H. albersiana or loxodon. The tooth within the base is 

 stronger and more deep-seated than in the two last-named species. 

 There are usually visible faint traces of one or two brown bands 

 around the periphery. 



Var. HOLOSTOMA Pilsbry. PI. 19 figs. 34, 35. 



More coarsely striate than the type ; ends of the peristome connect- 

 ed by an elevated parietal lamina ; basal tubercle deep-seated, 

 rather elongated, not marked by a rugose spot outside. 



Alt. 62, diam. 11 mill. 



Turk's Island, Bahamas. 

 Probably a distinct specific type. 



H. SARGENTI Bland. 



Subperforate, globose-depressed, obliquely striated, thin, pale, 



