CUBAN SUBFAMILY CHONDROPOMINAE TORRE AND BARTSCH 317 



The type, U.S.N.M. no. 422735, was collected by Henderson and 

 Bartsch in the gorge of the Taco Taco River about a mile from its 

 entrance. It has 4.4 whorls remaining and measures : Length, 13.5 

 mm ; greater diameter, 10.8 mm ; lesser diameter, 7.0 mm. 



This species is a very perturbing element, for we are here un- 

 doubtedly dealing with a hybrid problem in which one extreme is ex- 

 emplified by the above description, and since a large number of in- 

 dividuals in our series represent this type, we are bestowing upon 

 it the name perturhata. There are intergrades between this and the 

 openly umbilicated C. {Plicathyrella) claudicans (Poey), and the 

 range of color variation extends from the picture portrayed in our 

 description to that of the dark form of typical G. (P.) claudica7is. 

 It is doubly interesting since two of the subgenera, namely, Ghondro- 

 thyreJla and Plicathyrella^ find representations in the hybrid complex. 



CHONDROTHYRELLA (CHONDROTHYRELLA) EXCISA (Gundlach) PfeiSfer 



Plate 24, Figure 1 



1863. Chondropoma excisum (Gundl.\ch) Pfoffeb, Malakozool. Blatter, vol. 10, 

 pp. 187-188. 



Shell very broadly ovate, pale yellow, with interrupted spiral 

 bands of brown. The elements composing these bands are arranged 

 in both axial and spiral series. Nuclear whorls decollated in all 

 our specimens, a portion of the last volution only remaining, whioh 

 is smooth except that at its termination it shows the beginning of the 

 axial sculpture of the postnuclear turns. Postnuclear whorls strongly 

 rounded, appressed at the summit, marked by slender, almost sub- 

 lamellose, closely spaced, retractively slanting axial riblets, which 

 are a little more distantly spaced on the early turns than the later. 

 These riblets on the last whorl are separated by spaces about the 

 width of the riblets. The spiral sculpture is very feeble on the first 

 of the postnuclear whorls and slowly increases in strength with the 

 succeeding turns. The spiral threads are considerably stronger than 

 the axial lamellae and render these wavy. Of these spiral threads, 

 8 are present on the second, 18 upon the third, and the last between 

 the summit and the suture. On the last turn the intersection of the 

 spiral threads with the axial riblets produces alongated oval tubercles, 

 which have their long axis parallel with the axial sculpture. Periph- 

 ery inflated, strongly rounded. Base short, inflated, broadly um- 

 bilicated, well rounded, and marked by the continuations of the 

 axial riblets and 20 spiral threads, equaling those of the anterior por- 

 tion of the last whorl in strength and spacing. Within the umbilicus 

 the spiral sculpture appears to be absent, at least as far as can be seen 

 through the slit when it is open. Aperture very broadly oval; 

 peristome double, the outer broadly expanded, almost flattened. 



