208 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



marked by spiral threads a little stronger than those on the spire and 

 the feeble axial hair lines. The last whorl is solute for about one-fifth of 

 a turn. Aperture quite oblique, ovate, with a conspicuous auricle at the 

 posterior angle. Peristome double; the two fused on the outer lip and 

 coextensive. On the inner lip, particularly on the parietal wall, they ap- 

 pear more distant. 



This species ranges through the northeastern half of the Caicos atoll. 



I am recognizing two subspecies, which the following key will help 

 to differentiate : 



KEY TO THE SUBSPECIES OF CHONDEOPOMA (CHONDROPOMA) NECOPIUM 



Shell elongate-ovate necopium 



Shell ovate auspicatum 



CHONDROPOMA (CHONDROPOMA) NECOPITJM NECOPIUM, new subspecies 



Plate 34, Figure 6 



This race ranges from Grand Caicos south through East Caicos to 

 South Caicos. It is distinguished from Chondropoma (Chondropoma) 

 necopium auspicatum in having a more slender shell with less inflated 

 whorls and in having the nodules at the summit more pronounced. The 

 last whorl is also a little more widely solute. 



The type (U.S.N.M. No. 469138) comes from a rocky hill at Light- 

 born Creek on the south side of the salt pond on Grand Caicos, where 

 we collected hundreds of specimens. It has 3.9 whorls remaining and 

 measures: Length, 14. i mm.; greater diameter, 7.8 mm.; lesser diame- 

 ter, 6.0 mm. 



U.S.N.M. No. 391531 contains 645 topotypes from the same source. 



U.S.N.M, No. 391360 contains 2 specimens collected by Bartsch on 

 the east side of Little Halfway Creek, Grand Caicos. 



U.S.N.M. No. 390474 contains 53 specimens collected by Bartsch 

 from Stubb's guano cave at Cape Comete, East Caicos, Caicos Island 

 group. 



U.S.N.M. No. 391241 contains 17 specimens from Jones Hill, Cape 

 Comete, East Caicos, Caicos Island group. 



U.S.N.M. No. 391558 contains 52 specimens collected by Bartsch at 

 Bell's Cay, Cape Comete, East Caicos, Caicos Island group. 



U.S.N.M. No. 391546 contains 80 specimens from a hill on the west 

 end of East Caicos, collected by Bartsch. 



U.S.N.M. No. 391462 contains 25 specimens collected by Bartsch on 

 the west side of a hill facing the Salt Pond on South Caicos. 



CHONDROPOMA (CHONDROPOMA) NECOPIUM AUSPICATUM, new subspecies 



Plate 34, Figure 3 

 This race we found on Big Iguana Cay, off Cape Comete, East Caicos, 

 and also at the north end of Six Hill Cay opposite South Caicos. Al- 

 though these two localities are some distance apart, we were unable to 



