THE CYC[LOPHORID LAND M0LLUSIK9 OF AMIEEICiA 63 



CROCIDOPOMA (CROCIDOPOMA) VORTEX (Weinland) 



Shell small, almost lenticular with a thin yellowish-brown perio- 

 stracum, which is usually worn on the keels, exposing them as white 

 lines. The denuded shell is white. Nuclear whorls 1.5, strongly 

 rounded, smooth. The postnuclear whorls are well rounded and 

 marked by elevated spiral keels, of which 6 are present between the 

 summit and the suture on the first turn and 7 on the remaining whorls. 

 On the last half of the last turn there are usually intercalated threads. 

 Periphery well rounded. Base well rounded and marked by 5 strong 

 keels between the periphery and the edge of the umbilicus, 5 more 

 being present on the umbilical wall. The umbilicus is open and the 

 whorls can be seen within. Aperture very slightly oblique, circular ; 

 peristome rendered sinuous by the spiral cords. Operculum typically 

 crocidopomid. 



The species is restricted to the southwestern peninsula. 



We are recognizing two subspecies, which the following key will 

 help to differentiate : 



KEY TO THE SUBSPECIES OF CROCmOPOMA VORTEX 



Shell lenticular vortex 



Shell depressed-helicoid elevatum 



CROCIDOPOMA (CROCIDOPOMA) VORTEX VORTEX (Weinland) 



Plate 11, Figures 13-15 



1862. Cyclostoma vortex We3NLand, Malak. Blatter, vol. 9, p. 90. 



1869. Cyclotus vortex PrEarFER, Nov. Conch., vol. 3, p. 445, pi. 98, figs. 17-20. 



Shell small, almost lenticular, with a pale yellowish-brown peri- 

 ostracum, which when worn from the strong spiral keels leaves the 

 white shell below exposed. Nuclear whorls 1.5, strongly rounded, 

 smooth. Postnuclear whorls well rounded, marked by decidedly ele- 

 vated spiral keels, of which 6 are present between summit and suture 

 on the first turn, and 7 on the remaining turns. On the last half 

 of the last turn intercalated finer threads appear between the heavy 

 keels. In addition to the spiral keels the shell is marked by rather 

 strong incremental lines. The space between the very strongly ele- 

 vated keel near the summit and the summit of the whorl makes the 

 suture a deeply impressed channel. Periphery well rounded. Base 

 well rounded, marked like the spire, 5 strong keels being present 

 between the periphery and the edge of the umbilicus and 5 more on 

 the umbilical wall. The umbilicus is broad and extends to the very 

 first whorl. The last turn is solute for about one-twentieth of a 

 turn. Aperture very slightly oblique, circular; peristome ren- 

 dered slightly sinuous by the spiral cords and somewhat notched by 



