THE NAUTILUS. 



3 



arranged somewhat like the teeth of a comb, marginals also 

 comb-like, cusps not (usually) extending to the basal line. 



Genus Ferrissia Walker. 

 Ferrissia Walker, Naut., XVII, 1903, p. 15. 

 Type, Ancylus rivularis Say. PI. 2, fig. 3. 



Subgenus Lsevapex Walker. 



Lsevapex Walker, Naut., XVII, 1903, p. 15. 



Type. Ancylus fuscus C. B. Adams. Example, Ferrissia 

 (Lavapex) diaphana (Hald.). PI. 2, fig. 4. 



For reasons stated elsewhere (Naut., XXVI, p. 117), I can 

 not follow Hannibal in subordinating Ferrissia to Lcsvapex. I 

 agree fully with Gwatkin (J. of Con., XIV, 1914, p. 147), that 

 Ferrissia represents the most primitive type of radula, so far as 

 yet known, in the Ancylidce. The world-wide distribution of 

 the genus is evidence tending in the same direction. Lsevapex 

 is restricted to America and is, to my mind, clearly an offshoot 

 from the more ancient Ferrissia stock. In addition to its pecu- 

 liar shell characters, there is some evidence tending to show a 

 slight divergence also in the character of the lateral teeth, but 

 hardly sufficient to justify its generic distinction. 



Genus Gundlachia Pfeiffer. 



Gundlachia Pfeiffer, Zeitschr. fur Malak., VI, 1849, p. 98. 

 Type, Gundlachia ancyliformis Pfr. PI. 3, fig. 1. 



Poeyia Bgt., (1862), and Kincaidella Hann., (1912), are 

 synonyms, being based on immature or non-septate stages, but 

 the latter name may be retained for the group with striate apices. 



Gundlachia, like Ferrissia, includes two groups characterized 

 by the presence or absence of radial sculpture on the apex. 



I have examined all of the described species except G. cre- 

 pidulina Guppy from Trinidad and G. lucasi Suter from New 

 Zealand. 



Sub-genus Gundlachia s. s. 

 Apex smooth, except for light concentric wrinkles. Type, 

 Gundlachia ancyliformis Pfr. , Cuba. 



The following species also belong in this group: 



