CUBAN ANNUUARiroAE TORRE AND BARTSCH 219 



broadly expanded at the summit. These riblets are more closely- 

 approximated at irregular intervals, which condition gives a some- 

 what varicial appearance to the shell. The spiral sculpture consists 

 of spiral thi'eads, which vary considerably in strength in the different 

 races; in some races they are scarcely apparent, while in others they 

 are quite conspicuous. The junctions of the axial riblets and spiral 

 threads do not form conspicuous nodules, but the spiral threads 

 render the axial riblets wavy. Suture strongly constricted. Periphery 

 of the last whorl inflated, well rounded. Base short, inflated, well 

 roimded, openly umbilicated, marked by the continuations of the 

 axial riblets, which here become very much intensified, and which 

 are almost broken up into squamae by the spiral sculpture. This 

 condition is particularly pronounced immediately behind the aperture, 

 where each lamella terminates in a series of scallops. This character 

 is also a variable one, finding different expressions in the different 

 races. The last whorl is disjunct for a varying distance, depending 

 upon the subspecies. Aperture subcircular ; peristome double, the 

 outer moderately, broadly expanded, a little wider on the parietal 

 wall and the inner lip than on the rest of the shell. In some of the 

 races the parietal outer peristome is appressed to the preceding turns; 

 in others it remains disjunct. Inner peristome stronger exserted and 

 slightly reflected. A breathing pore opens on the inside of the parietal 

 wall at some little distance behind the aperture, near the posterior 

 angle of the aperture. This pore communicates with a tube, which 

 is located in the posterior angle and which extends backward for 

 more than 3 whorls. It then communicates by a slender cleft Avith 

 the hollow axis, thi'ough which breathing is evidently effected when 

 the operculum is closed. Operculum consists of many strongly raised, 

 retractively ciu"ved lamellar ribs, which extend completely across the 

 turns. These lamellar ribs are high at their inner edge, from which 

 they pass down in a gentle curve, rising again to the highest altitude 

 at their outer border, where they become fused into the spiral lamellae, 

 which project almost as far as the basal chondroid plate at the edge of 

 the operculum; the lateral margin of the operculum is strongly 

 channeled. 



This species is widely distributed through the Province of Pinar 

 del Rio, occurring almost on every exposed lump of limestone from 

 Guane eastward to Rangel and Rio Santa Cruz. 



The peculiar development of the breathing apparatus defines a very 

 distinct group, which we recognize as a single species. This species 

 breaks up into a series of geographic races, upon which we shall bestow 

 subspecific rank. 



