MOLLUSCA. 



Young Shell 



Young Shell. 



Adult Shell. 

 Pyprsea Exanthema. 



Argonauta Argo. 



Adult Shell. 

 Pteroceras Scorpio. 



In the class, called Gasteropoda from something like a foot, adapted to locomotion, proceeding from the 

 belly, the distinctive characteristics of the Mollusca are most prominently displayed, that is the high de- 

 velopement of the nutritive apparatus, with very imperfect locomotive powers. In the more perfect of them 

 we find a distinct head, furnished not only with feelers, but with eyes, and the rudiments of smell and hear- 

 ing. They can crawl from place to place, and many of those inhabiting the water can swim rapidly. Gene- 

 rally they are univalve, but occasionally multivalve. Their shell, as in other classes, is secreted from the 

 mantle, and is enlarged as the animal grows. The forms of the shell vary extremely in the several sub- 

 divisions. 



We present on this page some specimens of the Gasteropoda, namely, the Murex Tenuispina; the 

 Pteroceras Scorpio ; and the Cypraea Exanthema. 



Bulla is the name of a genus of Molluscs. Of some of its principal varieties we proceed to give a brief 

 account. 



In the Bulla Fragilis the shell is ovate-oblong, very thin and fragile, of a horn-color, with very small 

 transverse stripes, and with an apex rising into the rudiment of a projecting spire. It abounds in the 

 English Channel, near Nantes and Noirmontiers. 



In the Bulla Velum the shell is very delicate, of a light horn-color, with a snow-white band about the 

 middle, bordered on either side by a dark-brown one, and with white apex and base, both bordered with 

 dark-brown bands. 



In the Bulla Ampulla the shell is egg-shaped, and verging on the globular, beautifully mottled with 

 white, plum color, and reddish. It is said to exist in both the Indian and American oceans. 



Murex Tenuispina. 



Bulla Fragilis. a Shell, c Spiral End. B Anir 



(-368^1 r^J 



