165* 



wards the umbilicus, and at length forming another lobe nearly 

 covering the umbilicus, whose margin is angular ; operculum 

 horny, multispiral. 



Larger, more solid, and smoother than C. auriculatum, and 

 differing from that species hi its much thicker, revolute peritreme, 

 forming two distinct lobes, one of which nearly covers the um- 

 bilicus. 



West Indies. Mm, Cuming. 



193. Cyclostoma decussatum (Tab. Suppl. xxxi. a, f. 300, 

 301), nobis. 



C. testa oblonga, pyramidali, fusca seu fusco-nigricante decus- 

 satiin sulcata ; apice decollato ; anfractibus quatuor, rotundatis ; 

 sutura valida, crenulata ; apertura subelliptica, peritremate duplici, 

 interno tenuiusculo, sublevato, cxterno latiusculo, refiexo, umbili- 

 cum parvum subtegente. 



Shell oblong, pyramidal, fuscous or blackish, decussately 

 grooved, with an obtuse decollated apex ; volutions four, rounded ; 

 suture distinct, crenulated; aperture somewhat elliptical, slightly 

 acuminated posteriorly ; peritreme double, inner narrow, slightly 

 elevated, outer rather wide, reflected, partly covering the small 

 umbilicus. 



West Indies. Mus. Cuming. 



194. Cyclostoma Copanense (Tab. Suppl. xxxi. b, f. 310, 

 311), nobis. 



C. testa, acuminato-turrita (plerumque decollata), kevi, tenuis- 

 sime striata, nitida, olivaceo-fulva ; spira elongata ; anfractibus 

 sex, rotundatis ; sutura distincta ; apertura circulari j peritremate 

 duplici, interno tenui, angusto, porrccto, ad ultimum anfractum 

 interrupto, externo lato, lamellari, extenso, subinflexo, ad ulti- 

 mum anfractum porrecto, eniarginato, flexuoso ; umbilico mediocri, 

 extus carinato; operculo corneo, multispirali, lamelloso, intiis 

 stylo brevi, central], margine incrassato. 



Shell acutely turreted (usually decollated), very finely longitu- 

 dinally striated, but smooth and somewhat shining, of an oliva- 

 ceous fulvous colour ; the remaining volutions of the lengthened 

 spire after decollation are in general six ; they are rounded, and 

 the suture is distinct ; aperture circular, with a double peritreme, 

 the inner of which is thin, narrow and projected forward, and 

 interrupted at the last volution ; the outer is broad, lamellar, 

 spreading, slightly inflected, and flexuous, notched and projected 



