THE NAUTILUS. 67 
same way as the epiphragm of the Helices. In the following spring 
—the period of greatest activity in growth with all the fresh-water 
Pulmonates—the animal throws forth its newer and larger shell, 
retaining the older one on its back for the protection of its more 
tender viscera.” 
I regret that I can give but a meagre account of the soft parts. 
My only material was some specimens procured at Adelaide, which 
died on the voyage to Sydney, and were hastily and badly preserved 
on board the steamer. * * * Part of the liver and the herma- 
phrodite gland are pinched off into a sort of tail, which occupies 
the primary shell. With this exception, as Gundlach and other ob- 
servers have remarked, there is no difference from Ancylus. ‘The 
form and disposal of the stomach and intestines seemed, as well as I 
could ascertain, to agree with those of Ancylus figured by Moquin- 
Tandon. 
Jaw extremely minute and frail, about $ the length of the radula, 
very narrow, composed of a great number of separate imbricating 
plates, which appear to be arranged two deep, in contact but un- 
attached; each is oblong in shape and serrate at one end, resem- 
bling somewhat the scales on some butterflies’ wings. 
The difficulty of observing this tender and incoherent organ will 
account for the uncertainty that prevails regarding it. Troschel 
saw it, described it, and then unfortunately concluded that it was a 
piece of hardened skin. Stimpson failed to find it. Johnston 
noticed it in G. petterdi. In Latia Hutton asserts (Trans. N. Z. 
Inst., XIV, p. 156) that no jaw exists; it has more probably been 
overlooked. 
Radula a narrow parallelogram, very small, measuring about 3 
< 1 hundredths of an inch. Formula, 70 rows of 8:12:1:12:8. 
Each half row straight, meeting at a low angle in the centre. 
Rachidian with a long, slender basal plate, rounded and slightly 
expanded posteriorly ; reflection about a fifth of total length, bi- 
cuspid. Laterals with broad basal plates, emarginate at the prox- 
imal posterior corner, sloping away from the rachidian, reflection 
somewhat pyriform, the wide end proximal, set aslant on the basal 
plate and armed with a large proximal and two minor distal cups. 
Marginals more upright, with reflection of same pattern, but extend- 
ing almost the length of the basal plate. 
Conctusion.—The genus Gundlachia contains four American— 
G. ancyliformis, meekiana, californica, crepidulina—and two Aus- 
