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Phylum ANNULATA 



The Segmented Worms 



Bilaterally symmetrical animals with the body composed of 

 similar segments or metameres, without jointed legs, and with an 

 alimentary canal furnished with two openings. Only one of the 

 classes discussed in this course. 



Class Hirudinea — Segments of body marked externally by secondary 

 rings. Each end of the body is furnished with a sucker. The 

 medicinal leech is an example of this class. 



Phylum ARTHROPODA 



See Comstock's "Manual for the Study of Insects" and "The 

 Spider Book." 



Bilaterally symmetrical animals in which the body is segmented 

 and bears a pair of jointed appendages on each or on some of the 

 segments. 



Class Crustacea — The members of this class are aquatic Arthropoda, 

 which breathe by true gills. They have two pairs of antennae 

 and at least five pairs of legs. 



Class Arachnida — The members of this class are air-breathing 

 Arthropods, in which the head and thorax are grown together, 

 forming a cephalothorax ; which have four pairs of legs fitted for 

 walking, and which have no feeler-like antennse. To this class 

 belong the spiders, ticks, mites, and others. 



Order Acarina — This order includes the mites; these differ from 

 other Arachnida in that the abdomen is fused with the cephalo- 

 thorax, giving the entire body a more or less saclike appearance. 



Class Myriapoda — This class includes the centipedes and the milh- 

 pedes, air-breathing Arthropoda in which the thorax and abdomen 

 form a continuous region, with from six to two hundred segments, 

 each bearing a pair of legs. 



Class Hexapoda— Air-breathing Arthropoda, with a distinct head, 

 thorax, and abdomen. They have one pair of antennee, three 

 pairs of legs, and usually one or two pairs of wings in the adult 

 state. This class is composed of the different orders of insects; 

 among these are the following : 



