138 THE NAUTILUS. 
under-world of floating lily-pads ; sometimes they are found on dead 
leaves in the water. The species of this group are mainly more 
fragile and depressed than those of the first group, and sometimes 
they are modified to correspond with their stations, as A. parallelus, 
living on narrow stems. It is evident that this difference of station 
means also more or less difference of food ; and it will be interesting 
to find whether there exists any corresponding divergence in the 
dentition. The importance of full information on the station of 
every lot of Ancylus collected, will be evident from the foregoing. 
Nearly all specimens when collected, are more.or less coated with 
foreign matter, sometimes calcareous, but generally ferruginous. 
This must be removed before the color and finer sculpture can be 
observed. By floating the shell a short time on the surface of a 
weak solution of oxalic acid, rinsing it in water and then brushing, 
it may readily be cleansed. Nearly all North American species 
are then seen to be a clear corneous-white tint; most of them have 
growth-lines only, a few have radial strie. Most of those species 
which have been described as dark colored, such as A. obscurus 
Hald., owe their color entirely to foreign matter, the shell itself 
being very pale. 
Exhaustive comparisons with specimens of all North American 
species, and the types or author’s examples of most of them, con- 
vince me of the novelty of the following species. 
Ancylus peninsule Pilsbry & Johnson, 7. sp. 
Shell thin and fragile, with much depressed, broadly oval contour, 
the obtuse, rounded summit somewhat to the right of and behind 
the middle. Anterior, posterior and right slopes of the low cone 
nearly straight; left slope slightly convex. Color light horny 
brown, with a suggestion of olive when cleaned, usually with a very 
light brownish coating in a state of nature. Surface with slight, 
fine growth-lines and close, fine and conspicuous radial striz. 
Length 7, width 5, alt. 1-7 mill., often larger. 
St. John’s River and other localities in Florida, usually in creeks, 
living on the foliage of aquatic plants. 
Somewhat like the northeastern A. fuscus, but readily known from 
all other species of the United States by its large size, broadly oval 
and depressed form, blunt apex, and the dense radial striation. 
Several Antillean and South American species are somewhat similar 
to this, but these large and depressed forms have the apex far more 
excentric. 
