PHYLUM ARTHROPODA 



615 



Order 2.— Diplopoda (Chilocjnatha). 



Progoneata with a body composed of a considerable number of 

 apparent segments, each of which, with the exception of the first 

 three, bears two pairs of legs. There 

 are no maxillipedes. 



This order includes the Millipedes. 



Order 3.--Symphyla. 



Progoneata in which there are not 

 more than twelve leg-bearing segments, 

 and in which there is only a single 

 pair of bi-anching trachese, the external 

 apertures of which are situated in the 

 head. Not more than three pairs of 

 jaws. Feet with two claws. 



This order includes only the two 

 genera Scolopendrella (Fig. 486), and 

 ^cutigerella. 



Sub-Class II.-OPISTHOGONEATA. 



Myriapoda in which the genital aper- 

 tures are situated at the posterior ex- 

 tremity of the body. 



Fic:. 48t). — Scolopendrella 

 immaculata. (From Leuck- 

 avt, after Latzel.) 



Order 1. — Chilopoda (Syngnatha). 



Opisthogoneata with numerous (15 — 173) trunk-segments, 

 each bearing a single pair of legs. Numerous tracheae opening in 

 pairs of stigmata on the sides of a number of the segments. 

 Four pairs of jaws, including a pair of poison-jaws. Feet with 

 a single claw. 



This order includes the Centipedes (Fig. 487) and Scutigcra. 



General Organisation. 



External features. — The head in the Myriapoda is as well 

 marked off as in an Insect ; it appears to be composed of about 

 four fused segments. The antenna; consist sometimes of many, 

 sometimes of comparatively few segments ; in Pauropus they are 

 branched. A pair of eyes, situated on the dorsal surface of the 

 head, consist of aggregations of ocelli except in Scidigera, in which 

 there are compound eyes, differing, however, in their structure 

 from those of Insects. There is a movable labrum, a pair of 

 mandibles, and two pairs of maxillce. The mandibles have no 



R r 2 



