196 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



CHONDBOPOMA (CHONDROPS) PLANAENSE, new species 



Plate 33, Figure 5 



The truncated shell is pupoid. The coloration varies from unicolor 

 flesh-color to pale brown, frequently banded with interrupted spiral 

 bands of dark brown or even spiral zones of brown. Aperture with a 

 brownish flush within and a pale peristome. Nuclear whorls almost 2, 

 inflated, forming a flattened mammillated apex. These whorls are fol- 

 lowed by a short space on the succeeding turn, which is marked by 

 closely spaced, retractively slanting, axial, hairlike threads, after which 

 the normal postnuclear sculpture becomes apparent. The postnuclear 

 whorls are moderately rounded, marked by rather strong, slightly re- 

 tractively slanting, low, rounded, axial riblets, which are gathered into 

 tufts at the summit. These tufts embrace a varying number of fused rib- 

 lets. The spiral sculpture consists of low, rounded, feeble threads of 

 about the same strength as the axial. Of these, lo occur between the 

 summit and the suture. They render the axial riblets feebly nodulose 

 and the spaces enclosed between the axial riblets and spiral threads 

 finely pitted. Suture moderately constricted; periphery well rounded. 

 Base moderately long, narrowly umbilicated, marked by a continuation 

 of the axial riblets and seven spiral threads. Within the umbilicus three 

 additional feeble spiral threads are present, as well as the continuation 

 of the axial riblets. Aperture ovate, slightly auriculate at the posterior 

 angle. The last whorl is adnate to the preceding turn. Peristome double ; 

 the outer and inner almost coextensive and slightly reflected and adnate 

 to each other. 



The type (U.S.N.M. No. 391762) was collected by Bartsch on the 

 east side of the western Plana Island. It has almost 4 whorls remain- 

 ing and measures: Length, 9.5 mm.; greater diameter, 5.1 mm.; lesser 

 diameter, 4.3 mm. 



U.S.N.M. No. 390889 contains 241 topotypes from the same source. 



This species suggests Chondropoma (Chondrops) rawsoni but can at 

 once be differentiated from this by its better-developed spiral threads. 



CHONDROPOMA (CHONDROPS) RAWSONI PfeilTer 



Plate ZZ, Figure 6 



1867. Chondropojna rawsoni Pfeiffer, Malak. Blatter, vol. 14, p. 166. 



1905. Rhytidopoma euploca Dall, Smithsonian Misc. Coll., vol. 47, p. 449, pi. 59, 



fig. 6. 

 1937. Chondropoma russelli Clench, Proc. New England Zool. Club, vol. 16, 



p. 67, pi. 3, fig. 3. 



Truncated shell subcylindric, varying greatly in color in different in- 

 dividuals. This ranges from unicolor flesh-color through pale horn-color 

 through pale brown. The shell, however, may be interruptedly spirally 

 banded or marked with continuous broad chestnut-colored bands as in 

 Clench's Chondropoma russelli. Nuclear whorls about 2, inflated, strongly 



