198 AMERICAN OPEAS. 



P. Z. S. 1859, p. 26; Monogr. vi, p. 98. Rumina cuencana 

 H. AD., P. Z. S. 1870, p. 375. 



This unfigured form may prove identical with, or a variety 

 of, 0. micra, which is known from Ecuador. The description, 

 given above gives no adequate ground for considering it a 

 distinct species. 



3. 0. GRACILE ( Button). PL 28, fig. 70. 



Cf. p. 125. This species occurs in tropical America in 

 forms indistinguishable from those of the Oriental region, 

 though Occidental specimens have usually been known as 

 0. subula Pfr. Its chief characters are the straight, high 

 spire, very equable and moderate convexity of the whorls, the 

 distinct, arcuate striation, usually appearing a little puckered 

 below the suture, and the long aperture. As in the Orient, 

 a slender and a stouter form may be recognized, usually oc- 

 curring together. Local variation is chiefly in size and num- 

 ber of whorls, different colonies in one general locality often 

 showing the extremes of variation, as in the following from 

 around Havana : 



Length 9, diam. 2.9, length aperture 2.9 mm., whorls 7% 

 (ElVedado). 



Length 11.5, diam. 3, length aperture 3.2 mm., whorls 8^/2 

 (Marianao). 



It often reaches a large size, quite equal to typical gracile, 

 some from Merida, Yucatan being 13.5 mm. long, with 9% 

 whorls. 



Distribution, entire West Indies; South America as far 

 as Para and Guayaquil ; Southern Mexico and Central Amer- 

 ica. I have examined specimens from the following places. 

 Cuba: Havana and environs, Formosa, Castillo de Jagua at 

 entrance of Cienf uegos Bay, Santiago. Haiti : Sans> Souci, 

 St. Mark, Port au Prince (Henderson and Simpson) ; Jeremie 

 "S. octonula" Weinland) ; Santo Domingo City (H. Prime). 

 Jamaica: Kingston (W. J. Fox). Porto E/ico: San Juan. St. 

 Thomas, St. Croix, St. Bartholomew, St. Johns, St. Eustatius, 

 Antigua, Guadeloupe, Barbados, Trinidad. Brazil: Para. 

 Venezuela: Maraeaibo (E. S. Penny, 1853). Colombia. Also 



