2 



THE NAUTILUS. 



fauna must for the present be based wholly upon the peculi- 

 arities of the radula and jaw. 



The arrangement of the Ancylidae proposed by Hannibal, 

 (Pr. Mai. Soc. Lond., vol. x, 1912, p. 147), is not based upon 

 any distinctions of systematic value. The genera and subgenera 

 arranged under the different subfamilies are entirely heterogen- 

 eous and in several instances genera and their subgenera appear 

 in different subfamilies. The whole arrangement is absolutely 

 futile and must be entirely disregarded. 



The arrangement that I would propose is as follows: — 



I. Subfamily Lax\cin^:, Hannibal. 



Jaw as in Lymnaea with two accessory plates. Radula also 

 Lymnaeid in character. Central tooth unicuspid or tricuspid, 

 laterals bicuspid w T ith large quadrate bases, marginals comb- 

 like, the cusps extending beyond the base. 



This group was proposed, but without any definition, by 

 Hannibal (Naut., vol. xxviii, 1914, p. 24). 



Genus Lanx Clessin. 

 Lanx Clessin, Con. Cab., Ancylinen, 1880, p. 10. 

 Type, Ancylus newberryi Lea. Example, Lanx patelloides 

 (Lea). PI. 2, fig. 1. 



Subgenus Walker via Hannibal. 

 Walkerola Hannibal, Pr. Mai. Soc. Lond., X, 1912, p. 149. 

 Type, Lanx ( Walkerola) klamathensis Hannibal, PI. 2, fig. 2. 

 Conchologically Walkerola appears to bear the same relation to 

 Lanx that Lxvapex does to Ferrissia. 



Genus Fisherola Hannibal. 

 Fisherola Hannibal, Pr. Mai. Soc. Lond., X, 1912, p. 151. 

 Type, Fisherola lancides Hannibal. 



Nothing has been published on the soft anatomy. It is 

 placed here on account of its size, shape and habitat. 



II. Subfamily Ferrissiinje, n. subf. 

 Jaw segmented in plates. Radula with a bicuspid central, 

 laterals obliquely reflected with from two to five small cusps- 



