234 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



which is rendered somewhat irregular by the siphon immediately behind 

 it; the inner peristome is slightly exserted and slightly reflected. Oper- 

 culum typically opisthosiphonid. 



This species occupies Little Abaco, New Providence, and Exuma 

 Islands of the Bahamas. I am recognizing three subspecies. 



KEY TO THE SUBSPECIES OF OPISTHOSIPHON (OPISTHOSIPHON) 

 BAHAMENSIS 



Axial sculpture stronger than spiral abacoellus 



Axial sculpture not stronger than spiral. 



Denticles at the summit exserted bahamensis 



Denticles at the summit not exserted exumaensis 



OPISTHOSIPHON (OPISTHOSIPHON) BAHA3UBNSIS ABACOELLrS, new subspecies 



Plate ZI , Figure 4 



1905. Opisthosiphon bahamensis Dall, Smithsonian Misc. Coll., vol. 47, p. 450, 

 in part. 



This subspecies is nearest related to typical Opisthosiphon (Opis- 

 thosiphon) bahamensis bahamensis (Shuttleworth), differing from this by 

 having the axial sculpture a little stronger and the spiral weaker. The 

 type has 56 axial riblets on the first, 78 on the second, 100 on the third, 

 and no on the last of the remaining turns. 



The type (U.S.N.M. No. 180684) was collected by Owen Bryant on 

 Little Abaco near Marsh Harbor, Bahamas. It has a little more than 3 

 whorls and measures : Length, 10.5 mm. ; greater diameter, 5.9 mm. ; 

 lesser diameter, 4.5 mm. 



U.S.N.M. No. 180683, contains 2 other specimens collected near 

 Nields, Little Abaco, one of which has a little over 3 whorls and meas- 

 ures : Length, 10.2 mm. ; greater diameter, 5.8 mm. ; lesser diameter, 

 5.1 mm. 



OPISTHOSIPHON (OPISTHOSIPHON) BAHAMENSIS BAHAMENSIS (Shuttleworth) 



Plate 37, Figures 8, 9 



1865. Ctenopoma bahamense Shuttleworth, Pfeiffer, Monographia pneumono- 



pomorum viventium, Suppl. 2, p. 115. 

 1905. Opisthosiphon bahamensis Dall, Smithsonian Misc. Coll., vol. 47, p. 450, 



in part. 

 1905. Chondropoma bahamense Johnson, Nautilus, vol. 19, p. 72. 



This, the typical subspecies, appears widely and abundantly distributed 

 over the Island of New Providence. It differs from Opisthosiphon 

 (Opisthosiphon) bahamensis abacoellus in having the axial sculpture 

 not stronger than the spiral, and from O. (0.) b. exiimaeitsis in having 

 the denticles at the summit exserted. 



The specimen figured (U.S.N.M. No. 183380) one of two which 

 come from Nassau, New Providence, has 58 axial ribs on the first, 76 

 on the second, and 86 on the last of the remaining turns. It has a little 



