44 STROPHOCHEILUS-TIIAUMASTUS. 



This group differs from the preceding subgenera in its simple, un- 

 expanded lip. A few forms of Dryptus, such as S. pardalis, connect 

 to some extent, the two groups. Thaumastus is most abundantly 

 developed on the eastern slope of the Andes in Peru, while Dryptus is 

 mainly a group of Venezuela and Columbia, Strophocheilus of Brazil, 

 and Borus covers practically the entire range of all the other 

 groups. 



It is a mere accident that the name Thaumastus is applied to this 

 group, the fact being that of the entire list given in Die Heliceen, 

 only one species the one designated as type belongs to the present 

 genus, the others being Bulimulidce. Thaumastus as here used is 

 therefore by no means equivalent to Thaumastus of former authors. 

 It is more nearly equal to Orphnus (a preoccupied name), but in- 

 cludes, as will be seen, some species referred hitherto to Scutalm, 

 etc. 



The species fall into four groups distinguished by the following 

 characters : 



a. Shell distinctly perforate or umbilicated. 



b. Large (alt. about 80 mill), solid, with dark lip and col- 

 umella, the body-whorl with some spiral series of grains, 



Group of S. melanocheilus. 

 bb. Usually smaller, without this special sculpture, 



Group of S. inca. 

 act. Shell imperforate. 



b. Nepionic whorls longitudinally rib-striate, 



Group of S. taunaisii. 



bb. Nepionic whorls thimble-pitted, Group of S. thompsoni. 

 As the apical sculpture of a considerable number of species is un- 

 known, some transpositions and other changes in this grouping will 

 probably be necessary. Moreover, many cabinet specimens are too 

 worn to show the true sculpture. 



Group of S. melanocheilus. 



Perforate, with dark peristome and columella, the surface with 

 some spaced spiral series of granules; nepionic shell closely waved- 

 striate. 



S. MELANOCHEILUS Nyst. PI. 23, figs. 62, 63. 



Shell perforate, lengthened-ovate, solid; chestnut brown, with a 

 darker girdle below the white-edged suture, bounded below by a 



