MYRIOPODA. 



533 



of long bristles above mentioned gives to the fossil the aspect of the 

 caterpillar of such a Moth as the Tiger-moth. 



Order II. Chilopoda. — This order includes the recent Centi- 

 pedes (fig. 436), characterised by their elongated depressed bodies, 

 each body-ring being protected by a dorsal plate above, and a cor- 

 responding ventral plate below. The first two pairs of thoracic 

 appendages are converted into foot-jaws, the second pair being of 

 large size and hooked, and being connected with poison-glands. 

 All the remaining body-rings carry a single pair of jointed legs each, 

 and the tracheal stigmata are usually placed on alternate segments. 

 The generative organs open at the posterior end of the body. 



With the exception of the problematical Geophilus proavus of 

 the Lithographic Slates (Jurassic) of Germany, the oldest known 



t&m^rP : > 



Fig. 43S. — A specimen of Palceocampa anthrax, from the Coal-measures of Illinois, 

 enlarged twice. (After Scudder.) 



remains of Centipedes are of Tertiary age. Most of these have 

 been found in amber, and they all fall under existing families of the 

 order. 



Order III. Archipolypoda. — This order has been founded by 

 Scudder for the reception of a number of Palaeozoic Myriopods, and 

 is characterised as follows : The body in the Archipolypoda is fusi- 

 form and elongated, composed of many segments, and thickest in 

 the anterior half or third. The cephalic appendages are borne upon 

 a single apparent segment. The body-segments are provided each 

 with a pair of ventral plates and a more or less divided dorsal plate. 

 " the latter occupying the upper surface and most of the sides of the 

 body, and divided more or less conspicuously into a ridged anterior 

 and a lower posterior portion, the anterior frequently bearing spines 

 or tubercles." The ventral plates are as broad as the body, each 

 bearing a pair of long corneous legs, approximated at the base, and 



