190 AMERICAN OPEAS. 



The locality was supposed by Pfeiffer to be the island 

 Opara, but no form similar to this has been found in Poly- 

 nesia. Pfeiffer 's description and figures agree fully with 

 Central American examples, such as that shown in pi. 27, figs. 

 44-46, from Polvon, Nicaragua. The shell is narrowly um- 

 bilicate, the columella being hollow and large throughout (fig. 

 44). The shape is characteristic, the upper third of the 

 length tapering conically while the rest of the shell is sub- 

 cylindric. It is very pale yellowish-corneous, somewhat 

 translucent, very glossy. The riblets are strong and regular 

 below the suture, which is crenulated by them, but become 

 weaker or even subobsolete downwards below the middle of 

 each whorl; and they often give place to striae on the last 

 whorl. Whorls Sy 2 to 9, strongly convex, the last rounded 

 below. The aperture is vertical. Columellar margin well 

 dilated. Length of figured specimen 9.1, diam. 3.5 mm. Pol- 

 von, Nicaragua. 



Further north, in the State of Vera Cruz, the shells are usu- 

 ally more slender and taper more regularly. The ribs are 

 strongly developed on the intermediate whorls, subobsolete on 

 the last one or two. Specimens from Mirador (pi. 27, fig. 55) 

 measure : 



Length 9.8, diam. 3 mm., whorls 9 l / 2 . 



Length 8.3, diam. 2.7 mm., whorls 9. 



Other lots before me from Orizaba, Antigua and Vera Cruz 

 are similarly sculptured though some of the shells are wider. 

 Strebel has treated in detail of the distribution and dimensions 

 of East Mexican specimens, and Von Martens also has entered 

 fully into its distribution. 



A large series from Carthagena, Colombia, are very small, 

 length 7, diam. 2.4 mm., whorls 8y 2 , in other respects being 

 typical, or with the riblets below the suture very short, the rest 

 of the surface merely striate, and the umbilicus smaller. 

 Similar lots are before me from Venezuela, Trinidad and 

 " Brazil." 



A series from Para, Brazil, consists of rather weakly sculp- 

 tured shells, reaching the length of 7 mm., with Sy 2 whorls. 



Barbados shells are 7 to 9 mm. long, with typical or weaker 

 sculpture and a small umbilicus. 



