CHAPTER III. 



SUB- KINGDOM, ANNULOSA. 



4J*THEOPODA ANNUL ATA ANNUL OID A MOLLUSCA COXCHIFERA GAS- 

 TEBOPODA PTEBOPODA TUNICATA CEPHALOPODA CEUSTACEA 

 ANNELIDA AEACHNIDA SUCTOEIA, ETC. 



E term Mollusc is derived from the 

 Latin, and signifies soft ; the body of 

 the animal being soft, fleshy, and partly 

 or entirely covered by a shell attached to it 

 by means of muscles. Their shells are of two 

 kinds ; those of an epidermal character being- 

 formed upon the surface of a filmy cloak-like 

 organ called a mantle, answering to the true 

 skin of other animals ; and those of a dermal 

 character being concealed within the sub- 

 stance of the mantle, and frequently moulded 

 into a great diversity of forms, and coloured 

 with various tints. 



The animals belonging to the molluscous 

 sub-kingdom are divided into the following 

 orders, viz. Polyzoa, Tunicata, Conchifera, 

 Gasteropoda, Pteropoda, and Cephalopoda; 

 of these, all, except the Tunicata and a few 

 of the Pteropoda, are provided with a hard 

 '( calcareous shell. In the first, the Bryozoa, 

 approximate so closely to Zoophytes, and 

 having been, until very lately, classified with them, we 

 have thought it more convenient to the microscopist to 

 retain them in the place assigned to them by Ehrenberg. 



>: 



