156 PROCEEDINGS OF THE NATIONAL. MUSEUM Vol.89 



rhytidopomid. The siphon starts unmediately behind the peristome 

 at the posterior angle of the aperture and it extends as a tapering 

 tube into the umbilicus, plugging the hollow axis; it is marked by 

 concentric ridges. 



The specimen described and figured, U.S.N.M. No. 386615, is one 

 of a large series collected by Bartsch on the shore of Canimar River at 

 the type locality, Fundador, Matanzas Province. It has 4.2 whorls 

 remaining and measures: Length, 8.4 mm.; greater diameter, 3.8 

 mm.; lesser diameter, 3.5 mm. 



We have it also from the Yumurl Valley at Matanzas. 



RHYTIDOPOMA WRIGHTIANUM ([Gundlach] Arango) 



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

 2, forming a somewhat mammillated apex, the whorls of which are 

 strongly rounded and microscopically granulose, with the last portion 

 of the last turn showing the beginning of the postnuclear sculpture. 

 Postnuclear whorls inflated, strongly rounded, marked by lamellar or 

 sublamellar axial riblets, which vary conspicuously in spacing and 

 strength in the different races. These ribs are strongly expanded at 

 the summit, where they frequently form conspicuous auricles, which, 

 when broken, prove to be hollow. The spiral sculpture is very vari- 

 able, ranging from obsolete to strongly lirate. Suture strongly con- 

 stricted. Periphery well rounded. Base short, inflated, strongly 

 rounded, marked by the continuation of the axial ribs and by feeble 

 or rather strong spiral threads, depending again upon the race in 

 question. The last whorl is always solute for about half a turn and 

 is strongly deflected. Aperture broadly oval; peristome double, 

 the inner moderately exserted and scarcely reflected; the outer ex- 

 panded, the amount of expansion varying in the different subspecies. 

 The breathing siphon has its beginning at the posterior angle behind 

 the peristome, tapering and reflecting into the umbilicus, which it 

 completely plugs; the breathing, therefore, when the operculum is 

 closed, is effected through the pore marking the hollow axis of the 

 shell at the decollated end. Operculum typically rhytidopomid. 



This species ranges from Cape San Antonio at the western end of 

 Pinar del Rio Province, eastward to Cayajabos, breaking up into 

 a number of subspecies, which may be distinguished by the following 

 key and descriptions: 



KEY TO THE SUBSPECIES OF RHYTIDOPOMA WRIGHTIANUM 



Outer peristome broadly expanded wrightianum. 



Outer peristome not broadly expanded. 



Outer peristome moderately expanded ottonis 



Outer peristome very narrow cabrasense 



