HISPANIOLAN AND BAHAMAN ANNULARIIDAE 5 



Subfamily Chondropominae Henderson and Bartsch 



1920. Chondropominae Henderson and Bartsch, Proc. U. S. Nat. Mus., vol 58, 

 p. 59. 



Annulariid mollusks whose shell ranges in form from turbinate to 

 elongate-conic. The axial sculpture may consist of strong ribs or range 

 from these to slender, almost lamellar riblets, or it may be reduced to 

 incremental lines. There is also a wide range of strength in the develop- 

 ment of the spiral sculpture, which may be confined to the umbilicus or 

 may cover the entire shell. Breathing devices are present in some groups 

 and absent in others. The chief character of the subfamily, however, 

 is found in the operculum, which consists of a thin, simple, chondroid 

 basal plate of several whorls, the outer edge of which may be faintly 

 upturned to form a very fragile, low, slender lamella, suggesting the 

 starting point of the subfamily Adamsiellinae. This is, however, usual- 

 ly soon brushed away, leaving the operculum as a plain plate. The 

 operculum has a deposit of fine calcareous granules, which may be very 

 slight or fairly strong, depending upon the species in question. 



Type genus: Chondropoma Pfeiffer. 



Genus CHONDROPOMA Pfeiffer 



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



Shell ranging in form from turbinate to elongate-conic; the sculpture 

 in varying intensity may consist of axial ribs only or of axial 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 developed 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 ob- 

 solete 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 species : Cyclostoma sagra Orbigny = Chondropoma (Chondro- 

 poma) pictum sagra (Orbigny). Selected by Petit in 1850. 



KEY TO THE HISPANIOLAN SUBGENERA OP THE GENUS CHONDROPOMA 



Axial and spiral sculpture obsolete Wetmorepoma 



Axial and spiral sculpture not obsolete. 



Axial threads fused to form tufts at summit Chondropomorus 



Axial threads not fused to form tufts at summit. 



Spiral sculpture confined to umblical wall Chondropomium 



Spiral sculpture not confined to umblical wall. 



Spiral sculpture present on umbilical wall and base. 



Chondropomella 



