The Doha of the United State*. 



131 



Art. XV. The Uolia of the. United States. By J. Grfen, M. D. 

 Professor of Ckemistn, in Jefferson Me.di, a! College, Pennsylva- 

 nia, Corresponding Member. 



The great analogy existing between the very limited number of 

 species which form the genus Dolium, seems first to have been 

 noticed by M. Dargenvillc. He accordingly classed them to- 

 gether — the Buccinum Dolium of Linne being its type. La 

 Marck, in his arrangement, preserved this genus. All the species 

 included in it, except perhaps the D. Pomum, which seems more 

 nearly allied to the genus Cassis, form a natural group. They are 

 all ventricose, inflated, and subglobular, The spire is usually 

 somewhat depressed, and the substance of the shell is uncommon- 

 ly thin and brittle. All of them yet known are covered with large 

 transverse ribs on the exterior surface, causing the interior to be 

 grooved or furrowed. The right margin of the aperture is denta- 

 ted or crenulated along its whole length ; sometimes the lip is re- 

 flected, and sometimes there is a callous ridge on its inferior side. 

 There is a notch or semicanal at the base inclining backwards. 

 Some of them attain a very large size, as the D. Gallea, which have 

 been found more than ten inches in diameter, the characteristic thin- 

 ness of the shell still remaining. The animal is said to have an 

 operculum, and to produce a beautiful colouring matter, secreted 

 in a little reservoir contained in its neck. 



La Marck describes but seven species. Our late lamented 

 friend, the Rev. D. H. Barnes, of New-York, has figured an 8th, 

 which he calls D. Dentatum ; it is a fine large species; but Mr. 

 Swainson, of London, seems first to have noticed it under the 

 name of D. Ringens. W e shall here describe a ninth species brought 

 from the Pacific, and said also to be found on our western coast. 

 The Dolium in English is sometimes called the Tun. 



Dolium Zonatum. New Species. Plate 4. 

 Shell ovate, thin ; inflated with about twenty flattened ribs, not 

 quite as broad as the intervals between them ; in these intervals 

 there are one or more elevated lines, often increasing in number as 

 they approach the spire, where the longitudinal striae give them a 

 granulated appearance ; colour a uniform chestnut brown or yel- 

 lowish, darker on the ribs, without markings, except some whitish 



