190 CERION, GROUP II. 



riblets ; last whorl more or less tapering below, ascending in front, 

 its last half sculptured with rather strong, narrow, widely-spaced ribs, 

 narrower and often doubled in number at the base. Cone of the spire 

 rather long and tapering. Aperture rounded-ovate, brown in the 

 throat, the lip arid teeth ivory-white. Peristome flanged and very 

 heavily thickened; parietal callus strong. Parietal and axial lamellae 

 strong and long. 



Length 31.2, diam. 13 mill.; length 27.7, diam. 12 mill, (types). 



Length 33.5, diam. 13.7 mill. ; length 26.5, diam. 11.7 mill. 



Length 28, diam. 12.7 (average shell). 



Little Cayman Island, west end. 



Strophia levigata MAYN., Contrib. to Sci. i, p. 12, pi. 2, f. 2, 2 b 



(April, 1889) C. levigatum P. & V., Proc. A. N. S. P., 1896, p. 



319. S. festiva MAYN., t. c., p. 17, pi. 2, f. 5, 5 b, 5 c. S. nitela 

 MAYN., t, c., p. 73, f. 8, pi. 7. f. 16, 16 a. S. acuta MAYN., t. c., p. 

 15, pi. 2, f. 4, 4 b.S. picta MAYN., t. c., p. 18, pi. 2, f. 6, 6 b. 



This species is separated from C. pannosum in its various forms 

 by the longer, more tapering cone of the spire, its smoothness, only 

 the first post-nepionic whorl being costulate, the latter half of the 

 last whorl again becoming more or less ribbed. In pannosum the 

 whole cone of the spire is ribbed, even when the cylindrical portion 

 is smooth, and it tapers more abruptly above, producing a shorter, 

 blunter cone. 



The above description, apart from these characters, applies to 

 typical levigatum only. The several colonies of the species, though 

 all within a radius of a few miles, show local differentiation in size 

 and coloration, as noticed below. 



Typical levigatum " occurs on the west end of Little Cayman 

 Island, very sparingly on the coast, and rather more commonly 

 among the low growth of trees in the interior." They occupy an 

 extent of country about 3 miles long and a mile wide. Specimens 

 occur in groups of 4 or 5 individuals, scattered at rather wide inter- 

 vals along the two paths that cross the key. 



Color-form festivum Maynard (PI. 27, fig. 21). Similar to levi- 

 gatum, but white, copiously maculate longitudinally with brown 

 above, gray and brown below. 30x12.5 mill.; 27.5x12.5 mill. This 

 is merely a mottled form of levigatam, probably not in any sense a 

 race. It occurred on the borders of two small fields or cultivated 

 areas, of perhaps a quarter of an acre each, on the western path 



