CUBAN SUBFAMILY CHONDROPOMINAE — TORRE AND BARTSCH 307 

 KEY TO THE SPECIES OF SUBGENUS PLICATHYRELLA 



Surface of shell filelike claudicans 



Surface of shell not filelike. 



Shell chestnut-brown tenebrosa 



Shell horn or straw-colored assimilis 



CHONDROTHYRELLA (PLICATHYRELLA) ASSIMILIS (Gundlach) Pfeiffer 



Shell varying from small to medium size in the different races, 

 ovate, usually horn-color, sometimes brown, almost always interrupt- 

 edly spirally banded with brown. Nuclear whorls about 2, inflated, 

 strongly rounded, microscopically granulose ; the initial portion of the 

 first turn dark brown, the rest horn-color, Postnuclear whorls very 

 strongly inflated and rounded, crossed by numerous more or less 

 crowded, retractively slanting, axial riblets that vary from threads 

 to slender low lamellae in the different races. The spiral sculpture 

 consists of threads, which are also quite variable in strength in the 

 divers races. The junction of these two elements renders the axial 

 ribs somewhat sinuose and feebly nodulose at their meeting. Suture 

 well constricted. Periphery and base inflated, strongly rounded, the 

 latter openly umbilicated and marked by the continuation of the 

 axial ribs and spiral threads. The last, however, are much stronger 

 about the umbilical region than on the posterior portion of the base. 

 Aperture very broadly oval ; peristome double, the outer broadly ex- 

 panded and reflected, more so on the inner lip than the rest, marked 

 by radial flutings and concentric lamellae. The middle of the outer 

 peristome of the inner lip bears a fold which in some of the races 

 almost amounts to a cut. The part posterior to this is reflected as 

 a flap over the umbilicus, partly covering, or at least shielding it. 

 Operculum thin, red or reddish, corneous with excentric nucleus, cov- 

 ered by a heavy deposit of fine calcareous granules. 



Of the animal of C. (P.) assimilis assirnilis Gundlach says ^: "Ani- 

 mal whitish, head with scarcely darker suffusion. Tentacles ochre 

 colored with gray tip." When at rest it suspends itself with a mod- 

 ately long thread. 



This species extends through the mountains of a considerable part 

 of eastern Pinar del Rio Province. It has been found from the 

 Sierra la Guira to Pan de Guajaibon east to Mogote de Soroa. 



Distribution of the subspecies of C. {P.) assimilis is shown in fig- 

 ure 98. 



• Malakozool. Blatter, vol. 10, p. 186, 1863. 



