CUBAN ANNUUIRIIDAE TORRE AND BARTSCH 223 



ribs. Peristome reflected, widely expanded, and somewhat fluted. 

 Operculum marked by retractivcly curved ribs, which do not extend 

 across the entire width of the whorls. The inner border of these ribs 

 is fused to form a lamella, which is a little higher than the ribs. The 

 outer border of the ribs become fused to form an enormously developed 

 lamella m the last turn, which is reflected inward, domelike, over the 

 operculum which it almost completely covers. This reflected lamella 

 bears fine corrugations on its surface. The center of the operculum is 

 decidedly concave. 



Type: Xenopoma hystrix ([Wright] Pfeift'er). 



KEY TO THE SPECIES OF XENOPOMA 



Spines small humboldtianum 



Spines large. 



Outer peristome broadly expanded on the parietal wall aguayoi 



Outer peristome not broadly expanded on the parietal wall. 



Umbilical wall with well developed spiral zones of spines.- hendersoni 

 Umbilical wall without well developed spiral zones of spines. 



Spines between summit and umbilicus, 4 hystrix 



Spines between summit and umbilicus, 9 spinosissimura 



XENOPOMA HUMBOLDTIANUM (Pfeiffer) 



Plate 19, Figure 8 



1867. Choanopoma humboldtianum Pfeiffer, Malakozool. Blatter, vol. 14, pp. 



150-151. 

 1898. Choanopoma (Blaesospira) humboldtianum Kobelt and Mollendorff, 



Nachr. Deutsch. Malak. Ges., vol. 30, p. 183. 

 1920. Xenopoma humholdtiana Henderson and Bartsch, Proc. U. S. Nat. Mus., 



vol. 58, p. 68. 



Shell broadly elongate-conic, flesh colored. Nuclear whorls decol- 

 lated in all our specimens. Postnuclear whorls inflated, strongly 

 rounded, marked by slender, raised, spinulose axial lamellae, between 

 which from 3 to 7 finer axial threads are present. Of the axial lamellae 

 20 are present in the specimen figured on the first of the remaining 

 turns, 30 on the second, 44 on the third, and 42 on the fourth These 

 lamellae bear rather fine, low, hollow spines, of which 3 are present on 

 the first and second, and 5 are upon the remaining turns between the 

 summit and the suture. Suture strongly constricted. Periphery in- 

 flated, strongly rounded. Base short, inflated, strongly rounded, and 

 marked by the continuation of the axial sculpture and by 4 slender 

 denticles on each lameUa, the fourth marking the outer boundary of 

 the umbilical waU being the strongest, while within the umbilicus 

 there are 11 spiral threads which, at their junction with the axial 

 lamellae, form slender nodules. The last whorl is solute for a little 

 more than half a turn. Aperture subcircular; peristome double, the 

 iimer slightly exserted; the outer broadly expanded on the outer and 



