226 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



The type ( U.S.N. M. No. 355525) was collected by Bartsch on the 

 edge of a pine coppice about one-half mile north and east of the western 

 end of South Bight on Mangrove Key, Andros Island, Bahamas. It has 

 a little more than 3 whorls and measures : Length, 8.8 mm. ; greater di- 

 ameter, 5.5 mm. ; lesser diameter, 4.3 mm. 



U.S.N. M. No. 269710, contains a topotype which has a little more 

 than 3 whorls and measures : Length, 8.6 mm. ; greater diameter, 

 4.6 mm. ; lesser diameter, 3.9 mm. 



This species is nearest related to Opisthosiphon (Opisthosiphon) 

 mayori, from which it is readily distinguished by the much closer ribbing. 



I take pleasure in naming this species for John Mills, of the Carnegie 

 Institution, whose helpfulness during my Andros exploration was greatly 

 appreciated. 



OPISTHOSIPHON (OPISTHOSIPHON) ANDBOSENSIS PUsbry 



Plate 35, Figure 8 



1930. Opisthosiphon androsense Pilsbry, Proc. Acad. Nat. Sci. Philadelphia, vol. 

 82, p. 298, pi. 30, fig. 9. 



Shell decollated; the whorls remaining are somewhat inflated and 

 well rounded. They are crossed by strong, slightly retractively slanting 

 axial ribs, which develop into strong hollow cusps at the summit. Of 

 these ribs 53 are present on the last turn. The spiral sculpture consists 

 of low rounded threads, of which seven are present between the summit 

 and the periphery; they are not all of the same strength. The space be- 

 tween the summit and the first spiral thread is about as wide as the 

 two spiral threads and their intervening space below it. The periphery 

 is well rounded. The base is moderately long, openly umbilicated, well 

 rounded, and marked by nine spiral cords. A number of feeble indica- 

 tions of spiral cords are present on the umbilical wall. Suture channeled. 

 Aperture oval, oblique ; peristome double. The inner peristome is slightly 

 exserted, reflected over and appressed on the inner lip. The outer peri- 

 stome consists of a series of lamellae and is much broader over the um- 

 bilicus than elsewhere. The siphon is backward directed and almost ap- 

 pressed to the preceding turn. The last whorl is solute for about one- 

 tenth of a turn and the posterior angle on the outside is rendered 

 strongly denticulated by the axial ribs. 



The type (Acad. Nat. Sci. Phila. No. 151789) has 3.8 whorls re- 

 maining and measures : Length, 8.6 mm. ; greater diameter, 5.0 mm. 

 Through the courtesy of Dr. Pilsbry I have been able to examine and 

 figure the type, which was collected by Maurice Black in gravel on the 

 shore of Stafford Lake, Andros Island. 



This species is nearest related to Opisthosiphon (Opisthosiphon) 

 mayori. It agrees with it in the strong ribbing and the solute last whorl, 

 but here the ribs are much more closely spaced than in that species. 



