THE CLASSIFICATION OF ANIMALS 



523 



Class I — Archiannelida. Primitive marine worms without 

 parapodia or setae. Example : Polygordius. 



Class II — Chaetopoda. Bristles along the body. Examples 

 are the earthworm or sandworm. 



Class III — Hirudinea. Without bristles and having suckers 

 at both ends of the body. Examples are the leeches. 

 Phylum VIII. M OLLUSC A (Lat., mo//^5 — soft). Soft-bodied 

 unsegmented animals, often provided with a shell which is secreted 

 by a part of the body. 



Class I — Gastropoda (belly-footed). With or without shells, 

 which, when present, are of one piece and coiled. Snails, whelks, 

 and slugs. 



Class II — Pelecypoda (hatchet-footed). Shells in two 

 valves or parts. Clams, oysters, scallops, and mussels. 



Class III — Cephalopoda (head-footed). Foot partly sur- 

 rounds head and bears tentacles or grasping organs. Squids, 

 octopuses, and cuttlefishes. 



Phylum IX — ARTHROPOD A (Gr., arthros — joint ; pous^ 

 foot). xAnimals are segmented, and have chitinous exoskeletons 

 and jointed appendages. They live in water, on land, in the air, 



This reptile is a legless vertebrate with a skin covering made of scalelike plates. 



