No. 2327. THE ANN ULARI I DAE— HENDERSON AND BARTSCH. 59 



Chondropominae, new subfamily. 



Shell ranging in form from turbinate to elongate-conic. The axial 

 sculpture may consist of strong ribs, or range from those to slender, 

 almost lamellar riblets, or it may be decidedly reduced. There is 

 also a wide range of strength in the development of the spiral sculp- 

 ture, 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, resides 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 Adamsiellinae. This is, however, usually 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. — OJwndro'poma. 



Genus CHONDEOPOMA Pfeiffer. 



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



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

 ture in varying intensit}^ 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 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 up- 

 turned 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 of the genus. — Cyclostoma semilahre Lamarck. Selected by 

 Dallin 1905. 



CHONDROPOMATUS, new subgenus. 



Shell of turbinate form, marked by strong axial ribs, between whicli 

 finer threads parallel to the ribs are present. The axial sculpture 

 extends into the open umbilicus, the wall of which is marked by 

 strong spiral cords. Operculum typically Chondropomoid. 



Type of the subgenus. — Chondropoma latum (Gundlach) Pfeiffer. 



The type species is the only one known of this group at present. 

 It comes from eastern Cuba. 



