which inhabit Jamaica. 161 



Named in honor of the Honorable Mr. Roberts of Jamaica, 

 to whom we are indebted for this and other interesting species. 



Cylindrella rosea, var. fortis. Shell as long as var. ma- 

 jor, (p. 21,) but with less diameter and more cylindric. 



Cylindrella zoxata. Shell cylindric in the lower two- 

 thirds, very robust : pink with a tinge of brown or purple, 

 with a pearl white zone along the suture ; pale brown in the 

 aperture : with an elegant silky lustre produced by crowded 

 oblique very fine striae : spire with the outlines convex in their 

 upper half; apex truncate with the loss of — whorls : whorls 

 remaining eight, moderately convex, slightly margined on the 

 lower side, with a moderately impressed suture : aperture 

 similar ta that of C. rosea, but more dilated in the lower part 

 of the left side, and with the lip less expanded. It resembles 

 C. cylindrus, but differs in always having a white zone, and 

 in being often tinged with brown ; it is much more robust : the 

 aperture of C. cylindrus is more like that of C. rosea than of 

 this shell. 



Length 1.18 inch ; breadth .41 inch. 



Cylindrella lata often occurs with a much elongate sub- 

 conic form. This variety may be designated by the name 

 PRODucTA. A specimen is 1,23 inch long and .34 inch broad. 



Under Cylindrella Maug-eri may be comprehended many 

 types, which differ in color, form, and sculpture. These vari- 

 eties are very local, being strictly limited to their several dis- 

 tricts. But many of these districts have two varieties. They 

 all conform with great exactness to a common type, which is 

 of much less than generic value. The very considerable num- 

 bers of each variety, their strict conformity to their respective 

 subtypes, and their geographical distribution, seem to indicate 

 a specific value in the differences between them. Yet the 

 number of types is so great and the differences between many 

 of them are so slight, that we may well hesitate to pronounce 

 No. 9—2. 



