76 FIB8T LESSON 8 IN ZOOLOGY. 



the moufh is surrounded with ten arms, proyided with 

 suckers, while the mouth is furnished with a pair of jaws 

 somewhat like a parrot's bill. The squids are very active, 

 and can dart rapidly backward by ejecting the water from 

 their siphon or funnel. They have large, well-developed 

 eyes, and the brain is large, and protected by an imperfect 

 gristly brain-box. The Octopus has eight arms. To this 



V? 



Fig. 80.— The whelk. Its tentacles and proboscis extended; a, egg-capsules; 

 6, embryo shell. (Natural size.) 



class, called Cephalopoda, also belong the chambered N^au- 

 tilus, and the paper Nautilus. 



Since their bodies are so soft, all univalve and bivalve 

 shell-fish, and certain other animals allied to them, to- 

 gether with the cuttles, etc., are called ''molluscs," from 

 the Latin mollis, meaning soft. Molluscs, then, are soft- 

 iodied animals, with a foot or creeping dish, and usually 

 protected by a shell. 



Classes of Mollusca. 



1. Shell bivalved LameHlibranchiata. Oyster, clam, etc. 



3. Shell univalve Oephaloplvora. Snails. 



3. Shell when present coiled; 



8-10 arms Ceplialopoda. Cuttle-flsh. 



Literature. — Article Mollusea, by E. R, Lankester, in Encyclo- 

 paedia Britannica. — Woodward's Manual of the Mollusea, 1868, 

 With the writings of Brooks, Ryder, Dall, Jackson, etc. 



