FEOM PLIOCENE CLAY BEDS IN COSTA RICA. 361 



more prolonged canal, and a smaller tooth on the inner lip. It is entirely unlike 

 any species known to me from the Caribbean region, either fossil or recent. 



C. BiSERiATUM, Gabb, n. s., PL 46, fig. 50. _ ly^cUlC'^ 'hAAH^c*- ^^vUy<?^ , 



Shell minute, spire elevated, sides flat, whorls numerous; each one ornamented 

 above by two strong beaded ribs placed close together, and on the lower part of 

 the whorl by two more distantly placed plain ribs. The lower of these forms the 

 lower angle of the volution, and the upper of the two beaded ribs of the succeed- 

 ing whorl is placed on its periphery, so that the suture appears to be on the upper 

 surface of the beaded rib. Mouth small, the inner face of the outer lip ribbed; a 

 heavy rib on the base of the shell, another on the middle of the columella, and two 

 or three fainter, twisted folds in advance. 



Figure. Highly magnified; actual length 5 mm, 



C. LiMONENSis, Gabb, n. s., PI. 46, fig. 5L 



Shell minute, elongated, slender, spire very elevated, sides slightly convex, as 

 are also the sides of the individual whorls. Volutions twelve, of which the first 

 four are nuclear and smooth. The others are ornamented by a series of longitudi- 

 nal and revolving ribs of about equal size so as to produce a decided clathrate 

 appearance of the surface. Of the revolving ribs there are three to a volution. 

 Aperture broad; columella encrusted, twisted, and bearing but one faint fold in 

 advance. Actual size 4 mm. 



Figures. Magnified a little over five lengths. 



C. Caribb^um, Gabb, n. s., PI. 46, fig. 52. 



Shell small, very elongated, increasing so slowly in diameter as to be almost 

 sub-cylindrical. Surface flat on the sides; each whorl bears two large beaded ribs, 

 or what might be better described as two rows of large rounded tubercles; these 

 are connected by elevated ridges both laterally and longitudinally, and close below 

 the upper one, on the longitudinal connections, is a series much smaller. The 

 lower angle of the whorl carries a plain rib, on the under and outer face of which 

 is the suture. Mouth small; columella carrying a couple of oblique folds in 

 advance. 



Fragment figured 5 ram. in length; with the missing part of the apex it must 

 have been 1^ to 8 mm. Although both this and C. hiseriatum are characterized 

 each by two heavily beaded ribs, their manner of disposition, and the supplement- 

 ary ornaments serve sufficiently to distinguish them, as well as do the details of 



the mouths. A glance at the figures renders confusion impossible. 



74 



