MALACOLOGY. 



changed ? Which is the THIRD SUB-KINGDOM ? What is said of their ex- 

 ternal form? Of the internal parts? What of the nervous system? Of 

 their organs of sense ? To what are the muscles attached ? How are the 

 animals enabled to crawl, swim, &c. ? Why are their motions very slow? 

 What is said of the organs of respiration ? Of the blood, stomach, &c. ? 

 What is meant by the mantle? How does it vary ? How is the skin in 

 many Mollusks protected ? Is the shell always external ? Wl at are those 

 called which have no shell? What those which have a shell? How is the 

 shape of the shell determined? Whence the divisions into UNIVALVES and 

 Bivalves? What other names have these divisions received? What is 

 said of them? What is said of the coloring of shells? Name the parts of 

 a Univalve Shell, &c. Give the explanation of Bivalve shells as furnished 

 by the text and Plate XVII ? What are fixed shells ? What are free 

 shells ? What other division of the Mollusks are given ? What is said of 

 the adaptation of the shell and habits of Mollusks to their respective situa- 

 tions ? In what climate are they most abundant and most brilliantly col- 

 ored? What is said of the number of species? 



