26 PROCEEDINGS OF THE CALIFORNIA 
On p. 174 of same volume, I referred specimens from Spokan River to 
A. patelloides Lea, by mistake for A. crassus. 
Gundlachia Californica Rowell. Two specimens found by me in 
a little sandy rivulet at Baulines Bay, appeared to be merely the common 
Ancylus fragilis, but some months after, in taking out the animal, I found 
that one had a ‘‘deck’’ covering nearly its whole aperture, exactly as in the 
*‘voung of (7. Stimpsoniana’’ figured by S. Smith in the Ann. N. Y. Lyc. May, 
1870. The other, though exactly similar above, is an Ancylus below! That 
from Merced Falls, mentioned in our Vol. IV, p. 154, differs in being much 
smaller and paler, as were the Ancyli found with it. Mr. Smith states that 
the animal of his was exactly like that of Ancylus fuscus, and Dr. Stimpson 
described the dentition as similar also, to that of A. rivularis. These facts 
seem to show that the forms called Gundlachia are only modifications of 
Ancyli, analogous to the thickening of lip observed in Physas that survive a 
winter or a dry season. Some individuals, better nourished than others, 
secrete so much shell as to nearly enclose themselves in their first year’s 
shell. In the following year they may continue to form shell, and thus make 
a two-storied Gundlachia from a one-storied Ancylus. Thus we see why the 
specimens of the former so much resemble those of the latter found with 
them, in the respective localities of each so-called species. 
Limnophysa Binneyi Tryon. Many specimens of this fine species 
were found by Mr. Dunn at the Cascades of the Columbia, with a Physa, 
apparently a large var. of P. diaphanda. 
Pomatiopsis intermedia Tryon. Found once near Clear Lake by 
Dr. Yates, and by mein a small spring near Saucelito, Marin Co., the last 
proved by the animal. 
Bythinella Binneyi Tryon. Ihave found what I suppose to be this 
near the summit of ‘‘ Black Mountain,’’ Santa Clara Co., over 1,500 ft. alt., 
in a cold mountain rivulet. Others from branches of Alameda Creek found 
by Dr. Yates, differ entirely in the animal from that of Pomatiopsis, but it 
externally resembles closely that of Amnicola, of which this is scarcely more 
than a subgenus. 
Cochliopa Rowellii? Tryon. Two fossil specimens from post-pliocene 
beds near Green Valley, Contra Costa Co., are so much like this species, as 
figured, that it may still exist in California, even though found at Panama 
also, as Mr. Tryon believes, from specimens received. Several Central 
American fresh-water shells seem to be identical with the northern, and a 
Tropical American Pompholyx is described as closely resembling that of 
California. 
Hydrobia Californica Tryon. After long search I have found 
specimens of a true Hydrobia in a very limited station at the head of a 
brackish creek on the south side of ‘‘Lake Peralta,’’ Oakland, where they 
occur on floating sticks. The shell described by me in Proce. Acad. Se. Phil. 
1872, as Assiminea Californica ‘Tryon,’ and mentioned in these Proceedings, 
