84 BULUETIOSI' 181, UNITED STATES MATEONIAIL MUSEUM 



Weak nodules not present on the upper surface of all 

 of last whorl. 

 Penultimate whorl with obliquely curved wrinkles. 

 Wrinkles retractively curved on anterior half 



of whorl lacteofluvialis 



Wrinkles protractively curved on anterior 

 half of whorl. 



Nodulose sculpture strong savannensis 



Nodulose sculpture weak orcutti 



Penultimate whorl without obliquely curved wrin- 

 kles. 

 Wrinkles on penultimate whorl arrow-shaped. 



Arrow-shaped wrinkles iwinting forward minor 



Arrow-shaped wrinkles pointing back- 

 ward. 



Shell decidely elevated magna 



Shell not decidedly elevated montegoensis 



Wrinkles on jDenultimate whorl not arrow- 

 shaped. 



Umbilicus very narrow vendreysi 



Umbilicus not very narrow subglobosa 



Nodulations absent on base campeachyi 



PTYCHOCOCHLIS CORRUGATIOR (Chitty) 

 P-LATE 13, FiGUKES 37-39 



1857. Cyclotus corrugatior Chittt, Proc. Zool. Soc. London, vol. 25, p. 149. 

 1899. Neocyclotus (Plectocyclotus) corrugatior Kobelt and Mollendobff, Nachrb. 

 deutschen malak. Ges., vol. 31, p. 136. 



Shell of medium size, depressed-helicoid. Nuclear whorls flesh 

 colored, the succeeding turns wood brown, the last one paler, with the 

 summit of the corrugations lighter than the rest of the shell. Peristome 

 and interior soiled bluish white. The nucleus consists of about 1 

 smooth well-rounded turn. The first 1^4 postnuclear turns are well 

 rounded and marked by slightly retractively curved axial riblets, which 

 are about half as wide as the spaces that separate them. The suc- 

 ceeding turns are also strongly rounded and marked by the continua- 

 tion of the axial riblets, which here are rendered irregularly disposed 

 by the strong rugations. Beginning with the third whorl and extend- 

 ing over the remaining turns, except the last half of the last whorl, 

 strongly raised, decidedly oblique, protractively slanting ridges make 

 their appearance. These ridges extend to about one-fourth of the 

 distance between the summit and the periphery anterior to the summit. 

 They are rendered slightly nodulose by the axial riblets. The last half 

 of the last turn is marked by nodules, which are not of uniform 

 strength or spacing, or the direction of slant. These are also rendered 

 more finely nodulose by the crossing axial riblets. The suture of all 

 but the last half turn is deeply impressed. In the last half turn the 



