2 STR0BIL0PSlDi3E. 



group. The mouth parts do not differ materially from some 

 Pupillidae. 



The shell, aside from its helieoid shape (not a character of 

 great importance), differs from all Pupillidse in the arrange- 

 ment of the lamellae and baso-palatal folds. In multidentate 

 Pupillidae the five primary teeth are always recognizable (see 

 diagram in Vol. XXV, p. vii) while in Strohilops only the 

 main parietal lamella and the columellar lamella can certainly 

 be said to correspond, and these are found in so many other 

 land shells that their occurrence is not especially significant. 

 It is possible, however, that upper and lower palatal folds of 

 Pupillidas are represented by teeth 5 and 2 of fig. 1, and the 

 basal fold by tooth 1. 



Lamellae -{ 



' Parietal 

 Interparietal 

 Infraparietal 

 Columellar 



I 



-- — Palatal 1 



folds. 



Basal 



Fig. 1. Section of last whorl of Strobilops at the internal barrier, 

 showing terminology of teeth. 



By the accelerated lamellse and folds of the shell, which 

 appear early in the neanic stage, Strohilops resembles various 

 Tomatellinidae (Manual XXII). In that family both pari- 

 etal and palatal folds or laminae are sometimes present in the 

 neanic stage. Various Pupillid genera also, such as Orcula 

 and Lauria, have apertural armature during the neanic stage, 

 described in this work, Vol. XXVII. Orcula has spiral pari- 

 etal and columellar lamellae but no basal or palatal folds. 

 Lauria has basal folds, but they are spaced, transverse bar- 

 riers, wholly unlike the adult basal or palatal armature of the 

 species, and differing equally from the folds of inmiature 

 Strohilops, which from their inception appear to develop con- 

 tinuously into those of the adult shell. It appears likely that 



