THE NAUTILUS. 131 



shells is rubbed off, showing the golden and silvery hues of the real 

 surface ; upper valve convex, lower valve flat, with an ovate aper- 

 ture which reaches the margin by a fissure. Diameter about one 

 inch. 



Habitat from Maine to Florida, but rare and local north of Cape 

 Cod. It is sometimes very abundant in R. I. and at other times 

 quite rare. Generally in the fall months it is seen adhering to small 

 stones between tides at Opponang in Greenwich Bay, but during the 

 rest of the year it is rare to find one near the shore, its station being 

 among oyster beds. When growing upon the valves of Pccten 

 irradians, as it does sometimes, the Anomia conforms to the shape of 

 the Pecten and is ribbed like that species. 



The Anomia ephippium of Linnseus is a very common European 

 shell, and the great naturalist was deceived in our American shell, 

 supposing it to be the same species, and called it by the same name, 

 giving as its habitat, Pennsylvania. All authors since have known 

 it under that name, even down to Dall's revision of the Mollusca of 

 Mass., Mar. 10, 1870, but Prof. A. E. Verrill has shown it to be a 

 distinct species and named it Anomia glabra, V., Am. Jour. Sci., iii, 

 213, 187-2. 



The shell described in Binney's Gould, second edition, under the 

 name of Anomia electrica, Linne, is found among oysters and is dis- 

 tinguished from A. glabia by its sulphur yellow color, its defined 

 edge and its very convex upper valve. It is generally distorted, 

 semi-transparent and not so scaly as the preceding species. I think 

 it is merely a variety, and the variety is much more common with 

 us than the type. 



Family Ostreidae. 



The oysters commenced in the Carboniferous and are found in 

 every age since to the present time. Some of the fossil oysters are 

 two feet in length. Of the living species, the most peculiar in its 

 habitat is the tree oyster, whieh grows upon the roots of the man- 

 grove. There is but one genus in this family and about 70 species. 



212. Ostrea borealts, Lam. 



Syn.: Ostrea Canadensis, Brug, Lam, Hanley. 



213. Ostrea Virginica, Lam. 



Syn.; Ostrea Virginiana, Lister, Sby, Gld.; 0. rostrata maxima, 

 Chem.; 0. elonyata, Solander. 



These two species are so variable in shape that it is impossible to 

 give an accurate description of them. They are very irregular and 

 inequivalve, the larger valve generally attached to some object and 

 the smaller one moving forward as the shell grows. 0. borealis is 

 obliquely rounded ovate, with short curved beaks, while 0. Virginica 

 is long and norrow, with long and pointed beaks. In both species 

 the large valve is the lower one and the upper valve is the smallest, 

 flatter and smoother; surface of borealis flaky, greenish, that of 



