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, aud sometimes 

 they are modified to correspond with their stations, as A. parallehis, 

 living on narrow stems. It is evident that this difference of station 

 menus 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 aud 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 strife. Most of those species 

 which have been described as dark colored, such as A. obscurns 

 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 peninsula; 1'ilsbry &. Johnson, n. 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 stria-. 



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. fiifim, but readily known from 

 all other species of the United States by its large size, broadly oval 

 aud 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 

 excenlric. 



