56 BULLETIN 181, UjSITED STATES NATIONAL MUSEUM 



AMPHICYCLOTULUS (AMPHICYCLOTULUS) RUFESCENS (Sowerby) 



Pi^\TE 10, Figures 4, 5 



1843. Cyclostoma rufescens Sowekby, Thesaurus conchyliorum, vol. 1, p. 94, pi. 24, 



figs. 36, 37. 

 1843. Cyclostoma rufescens Sowekby, Proc. Zool. Soc. London, vol. 11, p. 60. 



"Shell nearly orbicular, generally of a reddish colour, with a short 

 spire consisting of 4 rounded, spirally ridged and striated volutions ; 

 the ridges crenulated; suture deep; aperture circular, with a thin 

 sharp peritreme; umbilicus large. From Martinique, communicated 

 by L. T. Powis, Esq." 



I have not seen specimens that satisfy Sowerby's description and 

 figures which I have copied. 



Specimens of ^. (A.) acutiliratus (Drouet) vary considerably in 

 tuberculation of their spiral keels, and it is quite possible that 

 Sowerby's species represents merely an exaggerated form of Drouet's 

 A. {A.) acutiliratus. 



AMPHICYCLOTULUS (AMPHICYCLOTULUS) ACUTILIRATUS (Drouet) 



Plate 10, Figubes 1-8 



1859. Cijclophorus acutilirattts Drouet, Essai sur les mollusques terrestres et 

 fluviatiles de la Guyane frangaise, p. 89, pi. 3, figs. 42-44. 



Shell moderately large, openly umbilicated, varying in color from 

 pale yellow to bright red. Nuclear whorls 2.5, well rounded, smooth. 

 Postnuclear whorls strongly rounded, marked by exceedingly fine, 

 closely spaced, incremental lines, which give the surface a silky appear- 

 ance, and strong sublamellar keels, of which 5 are present between the 

 summit and the suture on the next to the last whorl, and 10 on the last 

 turn. These keels are not quite regular in strength and distribution. 

 They average from one-half to one-fourth the width of the spaces that 

 separate them. Suture channeled. Periphery rounded. Base with 

 the umbilicus about one-fourth the greater diameter. Base well 

 rounded, marked by 8 spiral cords. The umbilicus is bounded by a 

 strong lamella and on the umbilical wall, within the umbilicus, 6 addi- 

 tional spiral lamellae are present. Aperture oblique, circular; peri- 

 stome simple, rendered somewhat fluted by the spiral sculpture. Oper- 

 culum typically amphicyclotulid. 



The specimen described and figured, U.S.N.M. No. 535859, a female, 

 is one of five specimens collected by me at Colson, 14 to 15 km. north of 

 Fort de France, Martinique. This has 5.4 whorls and measures: 

 Height, 11.1 mm. ; greater diameter, 15.3 mm. ; lesser diameter, 12.0 mm. 



U.S.N.M. No. 393879 contains seven specimens from the same lo- 

 cality. 



