GUNDLACHIA. 267 



Ex. A. lacustris, Linnaus, pi. 84, fig. 6. Shell, V. 

 lacustris, fig. 6, a. 



The Acroloxi are dextrorsal Ancyli ; they differ, more- 

 over, in the form and arrangement of the teeth. They are 

 found adhering to the stems and leaver of aquatic plants in 

 ponds and rivulets. 



Species of Acroloxus. 



lacustris, Linn. Nuttallii, Hald. 



Moquinianus, Bourg. 



Genus LATIA, Gray. 



Shell half-ovate, spiral, of one or more rapidly-enlarging 

 whorls ; spire short, posteriorly reclined ; aperture very 

 large, ohlong ; basal margin with a thin, narrow, flat, hori- 

 zontal lamina occupying the hind half of the left side, the 

 left hinder edge bent down and produced into a broad 

 expansion on the right side. 



Syn. Pelex, Gould. 



Ex. L. neritoides, Gray, pi. 84, fig. 7. 



This genus is from New Zealand, and chiefly differs from 

 Ancylus in the transverse septum in the aperture of the 

 shell. The orifice of respiration in the animal is on the 

 right side, the eyes are on the outer base of the tentacles, 

 and there is no operculum. 



Genus gundlachja, Pfeiffer. 



Shell thin, ancyliform, non-spiral, obliquely conical ; apex 

 inclined backwards, basal side two-thirds closed with a 

 fiat, horizontal lamina ; aperture anterior, horizontal, semi- 

 circular. 



Ex. G. ancyliformis, Pfeiffer, pi. 84, fig. 8. 



