CUBAN SUBFAINIILY CHONDROPOMINAE TORRE AND BARTSCH 323 



ribs and finer axial threads or of axial ribs and spiral threads. All, 

 even those without spiral sculpture on spire and base, have spiral 

 threads on the umbilical wall. No special breathing device is de- 

 veloped in the members of this genus. The operculum is simple ; that 

 is, it consists of a chondroid plate made up of a varying number of 

 whorls, the outer thin edges of which are sometimes faintly upturned 

 to form a suggestion of an obsolete lamella. The outer surface of 

 the operculum has a deposit of calcareous granules, which is usually 

 very slight but in some species rather pronounced. In no instance 

 is this entirely absent. The position of the opercular nucleus, whether 

 excentric or subcentral, depends upon the shape of the aperture. 

 Type : Cyclostoma sagra Orbigny. Selected by Petit in 1850. 



KEY TO THE SUBGENERA OF GENUS CHONDROPOMA 



Junctions of axial ribs and spiral threads forming sharp cusps. 



Outer peristome broadly expanded Chondropomartes 



Outer peristome not broadly expanded , Chondropomisca 



Junctions of the axial ribs and spiral threads not forming sharp 

 cusps. 



Shell very broadly ovate Gutierrezium 



Shell not very broadly ovate. 



Axial ribs gathered into tufts at the summit of the whorls. 



Axial ribs threadlike; sculpture reticulated Chondropomorus 



Axial ribs sublamellar; sculpture vertebrated Ch.ondropom.odes 



Axial ribs not gathered into tufts at the summit of the 



whorls Chondropoma 



Subgenus Chondropoma Pfeiffer 



1847. Chondropoma Pfeiffer, Zeitschr. Malak., vol. 6, p. 109. 



Shell ranging in form from ovate-conic to elongate-conic. The 

 axial sculpture consists of ribs or riblets, which vary considerably 

 in strength in the different species. The riblets are never gathered 

 into tufts at the summit. The S!)iral sculpture is also quite variable, 

 but regardless of its strength it is found upon all parts of the spire 

 and base. The peristome may be simple or expanded. No breathing 

 device is present. Operculum typically chondropomoid. 



Type: Cyclostotna sagra Ovh\g\\y = Chondropoma {Chondropoma) 

 pictum sagra Orbigny. 



KEY TO THE SPECIES OF SUBGENUS CHONDROPOMA 



Axial sculpture stronger than spiral. 



Shell elongate-conic marginalbum 



Shell ovate. 



Suture strongly denticulate carenasense 



Suture not strongly denticulate obesum 



