156 BULTMULUS-SONORINA. 



ornithologists. The propriety or necessity of such changes is still 

 doubtful. 



While the costellate apex and internal lamina of Sonorina readily 

 distinguish the group from other American Bulimoid snails, certain 

 species of Neopetrceus (see pi. 32, fig. 33) alone approaching it, some 

 of the species of the subgenus Euryptyxis Fischer (Journ. de Con- 

 chyl., xxxvi, 1888, p. 317), a Buliminoid group of Arabia, Socotra 

 and Somaliland, are so similar in shell characters as to deceive the 

 very elect. These shells have a similar columellar plate within, and 

 nearly similar apical costulation. In Euryptyxis however thiscostu- 

 lation is absent from the first whorl or half whorl, and in the forms 

 most resembling Sonorina, such as E. labiosus Miill., revoili Bgt., 

 maunoirianus Revoil, etc., there is a heavy callus connecting the 

 ends of the peristome, with a slight vertical groove at its junction 

 with the outer lip. This particular structure does not occur in 

 Sonorina. In view then of the great resemblance of oriental and 

 occidental forms, and the slight, elusive nature of their differences, 

 can we believe the two groups to be fundamentally different in 

 genesis? It is here that the testimony of the soft anatomy is given 

 with no uncertain emphasis ; for Euryptyxis has the characteristic 

 genital complications of Pupidce (see Bourguignat, in Revoil, Faune 

 et Flore des Pays Comalis, p. 96), while in Sonorina the anatomy is 

 as unequivocally that of Bulimulus. 



Several species belonging elsewhere have been referred to the pres- 

 ent group. Misled by a false locality label, the writer described as 

 new, B. hypodon (Nautilus, x, p. 102, 1897 ; see pi. 21, figs. 5, 6, 7), 

 which upon mature study proves to be Euryptyxis labiosus var. 

 jehennei Petit, of Socotra ; while B. zeledoni Dall (Proc. U. S. Nat. 

 Mus., x vi, 1893, p. 644) is the unicolored form or variety of Drymceus 

 josephus (Angas). 



Key to species of Sonorina. 



(Not including lapidivagus, dentifer, subspirifer and dismenicus, 

 the internal characters of which are unknown). 

 I. Peristome but slightly expanded ; aperture contained 2? times 

 in alt. of the shell, rimatus, p. 157. 



II. Peristome reflexed ; aperture larger. 



a. Thin ; internal lamina corkscrew twisted, 



spirifer, p. 158. 

 a' '. Thick ; internal lamina nearly straight, 



orthelasmus, p. 159. 



