598 



ZOOLOGY 



SECT. 



CLASS III.-MYRIAPODA. 1 



The class Myriapoda, including the Centipedes and the Millipedes, 

 consists of tracheate Arthropoda, which present many features 

 of resemblance to the Insects. There is a distinct head, bearing 

 many- jointed antenna, a pair of eyes, and two or three pairs of 

 jaws ; the body is not distinguishable into regions, but consists 

 of a number of similar segments, each bearing either one pair of 

 legs or two pairs. A system of air-tubes or tracheae, similar to 

 those of Peripatus and the Insects, opens by a series of stigmata, 

 usually in considerable numbers, on the sides or lower surfaces of 

 the segments. 



A. DISTINCTIVE CHARACTERS AND CLASSIFICATION. 



The Myriapoda are tracheate Arthropoda in which there is a 

 head, bearing antennae and jaws, and a trunk made up of a number 

 of similar segments, provided with leg-like appendages. Groups 

 of ocelli are present on the head. 



Sub-Class I.-PROGONEATA. 



Myriapoda in which the genital apertures are situated far 



forwards towards the anterior end of the 

 body. 



ORDER 1. PAUROPODA. 



Progoneata with ten trunk-segments 

 and nine pairs of legs, one pair to each 

 segment except the first. Antennae with 

 several nagella. Tracheae not known. 

 The order includes only the two genera 

 Pauropus (Fig. 496) and Eurypauropus. 



ORDER 2. DIPLOPODA (CHILOGNATHA). 



Progoneata with a body composed of 

 a considerable number of apparent seg- 

 ments, each of which, with the exception 

 of the first three, bears two pairs of legs 

 and represents two true segments united. 

 493. scoiopendreiia There are no maxillipedes. 



This order includes the Millipedes. 



FIG. 



immaculata. (tfrora Leuck- 

 art, after Latzel.) 



1 As will appear subsequently, the class Myriapoda, as formerly understood, 

 comprises two groups which are separated from one another by such important 

 differences that they might very well be looked upon as constituting two 

 distinct and independent classes. The old class Myriapoda is retained here as 

 a matter of convenience, and the two constituent groups are ranked as sub- 

 classes. 



