396 THE MOUNTAIN. 



them, increasing in extent. This substance, which is concealed 

 in mantles in the animal, styled naked mollusk, when it 

 goes on to form a shell for use and protection, is called 

 Testaceous. The " variety in form, color, substance, bril- 

 liancy of shells, is endless." All styles of mastication and 

 deglutition exist in mollusks ; stomachs simple, multiple, or 

 provided with special instrumentalities. As animals, they are 

 but slightly developed, have little industry, and only pre- 

 served from annihilation by "fecundity and vital tenacity." 



By referring to the classification of Siebold, it will be 

 seen that he distributes the Mollusks into three classes, 

 namely, Acephala, Cephalophora, and Cephalopoda. 



Cuvier separated the Mollusca into six classes, namely, 

 the Cephalopoda, Pteropoda, Gasteropoda, Acephala, Bra- 

 chiopoda, and Cirropoda. 



CLASSES I. and II., or Cephalopoda and Pteropoda, exist 

 only in the sea. 



CLASS III. Gasteropoda. ORDER I. Pulmonea. Some 

 of this order are terrestrial, others aquatic, the latter of 

 " which are required to come to the surface of the water 

 they inhabit to breathe." Of the terrestrial Pulmonea the 

 mountain has many representatives. By consulting the 

 beautifully -elaborated monograph of Dr. Binney, on the 

 " Terrestrial Air-Breathing Mollusks of the United States," 

 in three volumes, and still not finished,* some conception 

 may be formed of the extent of this group of animals. 

 The following is his tabular classification of the Pneumo- 

 branchiate Mollusca : 



* It will give the naturalists of the United States much pleasure 

 to be assured that this splendid work is to be continued, and it is 

 hoped finished, by the industrious and accomplished son of Dr, Bin- 

 ney, "Win. G. Binney, of Burlington, New Jersey. 



