64 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 68. 



The group of Clwndrothyra canal iculata: 



Chondropomo hendersoni Torre Western Cuba. 



Chondropoma canaliculata (Gundlach) Pfeit'fer Western Cuba. 



Chondropoma deceplw Arango Western Cuba. 



Chondropoma hamlini Arango Western Cuba. 



CHONDROTHYRETES, new subgenus. 



Shell varving from ovate-conic to elongate-conic, marked by axial 

 and spiral threads. Peristome broadly expanded, notched or inbent 

 at the umbilicus. The breathing pore perforates the parietal wall a 

 little behind the peristome, and a little anterior to the posterior 

 angle of the aperture. In some of the members of this subgenus 

 the exterior ])erforation leads to the surface at the posterior angle of 

 the aperture: in others to the umbilicus; in the species which have 

 the umbilicus sealed with a callus the breathing pore communicates 

 with the exterior by means of the hollow axis and the opening at the 

 truncated summit of the shell. Operculum tyj)ically Cliondropo- 

 moid. 



Type of the subgenus. — Cydostoma s/iuitlewortM Pfcifl'er. 

 The followmg s])ecies are now referred to this subgenus. They 

 fall mto two groups as follows : 



The group of Ghondrotliy rates shuttlewortJd: 



Cydostoma sliuttltworthi Pfeiffer Western Cuba. 



Cydostoma shuUleiuorthi incrassatuvi (Wright) Pfeiffer Western Cuba. 



Cydostoma {Chondropoma) shuttleivorthi gundladd Arango Western Cuba. 



Chondropoma foveatum (Gundlach) Pfeiffer Western Cuba. 



Cydostoma ottonis Pfeiffer Western Cuba. 



Cydostoma daiidicans Poey Western Cuba. 



Chondropoma exdsum (Gundlach) Pfeiffer Western Cuba. 



Chondropoma unilabiatum (Gundlach) Pfeifl'er Eastern Cuba. 



Cydostoma tenebrosum Morelet Western Cuba. 



Cydostoma sericatum Morelet Western Cuba. 



Chondropoma assimile (Gundlach) Pfeiffer Western Cuba. 



The group of Chondrothyretes sinuosa: 



Chondropoma sinuosa (Wright) Pfeiffer Western Cuba. 



Chondropoma echinulata (Wright) Pfeiffer Western Cuba. 



Rhytidopominae, new subfamily. 



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

 sculpture may be axial ribs only, or axial ribs on the spire and base, 

 with spiral cords in the umbilicus, or axial and spiral threads on 

 spire and base. In strength the sculptural elements may vary in 

 different species from lamellar to obsolete. A breathing device may 

 be present or absent; these are discussed under the subdivision in 

 which they occur. The operculum in all forms has as a basis a 

 chondroid plate composed of a number of whorls. The outer edge 

 of these whorls is never upturned to form a strong lamella. The 



