

224 STAURODON. 



Genus STAURODON Lowe. 



Staurodon LOWE, Ann. and Mag. of Nat. Hist. (2), ix, 1852, 

 p. 278, for Pupa saxicola and P. seminulum. 



The shell is minute, oblong, the last whorl without crest. 

 Peristome continuous by a strong parietal callus. Teeth ar- 

 ranged as in Vertigo except that the angular lamella is tuber- 

 culiform, marginal upon- the parietal callus close! to the 

 termination of the outer lip, with or without a short con- 

 tinuation inward. 



Type Staurodon saxicola (Lowe). Distribution, Madeira, 

 See pi. 15, figs. 12-14, 



The emergence of the angular lamella and its union with 

 the outer lip is probably an ancestral character, found also 

 in Ptychalaea and some other Vertiginine groups, as well as 

 in other subfamilies, such as Gastrocoptinae. In Staurodon 

 this lamella has been much shortened, often running inward 

 less than shown in pi. 15, fig. 14. 



The genus has probably existed on Madeira since the early 

 Tertiary, as it appears to have no near relatives in the Euro- 

 pean series from the Oligocene on. The strong parietal callus 

 is doubtless a later development. Many snails of arid regions 

 show more or less similar strucures. 



In his publication of 1852, Lowe places only the species 

 Pupa saxicola and P. seminulum under Staurodon, but in his 

 differential diagnosis of saxicola he mentions P. (Vertigo) 

 alpestris and P. pygmaea in order to point out how saxicola 

 differs from them, but without stating or implying that they 

 belong to Staurodon. It appears from this that either saxi- 

 cola or seminulum must be the type of Staurodon. In 1854 

 Lowe designated P. pygmaea Drap. the type of Staurodon, 

 a course clearly barred by the fact that he had not included 

 this species in his group in 1852. 



1. STAURODON SAXICOLA (Lowe). PL 15, figs. 13, 14. 



The shell is shortly rimate, cinnamon-brown, oblong, taper- 

 ing slightly upwards, very finely but distinctly striate, the 

 striation strongest on the penult and antepenult whorls. The 





