14 8 l'KOCEp;DIi\GS OF THE MALACOLOGICAL SOCIETY. 



Genus Gundlachia, Pfeiffer. 



Gundlachia, Pfeiffer, 1850 {G. ancyliformis, Pfr.); Poeijia, Bour- 

 guignat, 1862 {P. gundlachoides, Bourg.).^ 

 Type, Gundlachia ancyliformis, Pfeiffer. 



Sub-genus Kincaidili.a, n. sub-gen. 



Type, AncyluH fragilis, Try on. 

 Ancyhis (sp.), Tryon, 1863 {A. fragilis, Tryon). 



Named after Professor Trevor Kincaid, who has kindly examined 

 this manuscript. 



Sub-genus Ivincaidilla. Shell small, averaging 3 mm. in diameter, 

 patelliform, high-arched, narrowly ovate-elliptical in outline, finely 

 radially and concentrically striate, apex prominent, decidedly sub- 

 dextral, distinctly posterior, and marked by fine concentric and 

 sub-spirally radial striae ; habitat lakes and streams. 



Sub-genus Gundlachia, s.s. Shell of small size, averaging 2 or 3 mm. 

 in diameter, growth during first year as in Kincaidilla\ as animal 

 nears adult condition, however, a septum develops, cutting off the 

 posterior half of aperture, succeeding growth crepiduliform ; habitat 

 chiefly sti'eams. 



Gundlachia, s.s., needs no introduction, since the group has been 

 a matter of discussion for some years, and it only need be noted 

 that several species from New Zealand, Trinidad, etc., referred here, 

 when the a[)ical sculpture and other characters are studied will 

 almost certainly be found to belong to distinct genera which have 

 reached this same stage of specialization. Kincaidilla is instituted 

 to receive certain Nearctic Gundlachias heretofore confused with the 

 Ferrissias, from which they differ in the narrowly elliptical outline 

 and high strongly inclined apex. None of the Ferrissias are known 

 to develop a septum either regularly or infrequently, but it is, 

 apparentlj', occasionally present in all the Kincaidillas. From septate 

 specimens of G.fragilis it appears that this may be due to syntonic 

 influence, at least in certain cases. 



Gundlachia (Kincaidilla) fkagilis (Tryon). 



Ancylus fragilis, Tryon, 1863; Gundlachia Californica, Howell, 186;; 

 (syntonic form) ; A. ^ patelloides, Lea ', J. G. Cooper, 1872. 



Shell minute, elongate, highly arched, apex prominent, decidedly 

 posterior and inclined ; habitat streams and (less frequently) ponds, 

 on sticks and submerged vegetation. 



Coast Range System. 



Genus Lanx, Clessin. 



Ancylus (Velletea) (sp.), Haldeman, 1844 {A. (V.) Nuttalli, Hald.); 

 Lanx, Clessin, 1890 [A. Xetoherryi, hea^ A. pafelloides, Lea). 

 Type, Ancylus patelloides, Lea. 



' Juvenile Gtcndlachia, vide Crosse & Fischer. 



