298 Mr. Newport on the Class My'riapoda, Order Chilopoda, 



agreement in their structure and mode of union to form the lip in Scolopendra, 

 IMhobius and Cermatia. 



This is the comparative anatomy of the head in Chilopoda ; and I trust that 

 I shall hereafter he able to demonstrate a precise agreement in the parts, and 

 their mode of union, in the Chilognatha and in the highest of the Articulata, 

 the hexapod Insects. 



Although it is not my intention at present to trace the union of the seg- 

 ments of the body through the genera of Chilopoda to the more perfect Hexa- 

 [>o(ls, I may simply remark that this union is based on precisely the same laws 

 in the body as in the cephalic region, — union in pairs. 



Generic and Specific Characters. 



The parts of the skeleton that afford generic or specific descriptions are the 

 antennae, the ocelli, the dental plates and teeth in the head, the number and 

 form of the segments and legs, the number, form and arrangement of the 

 spines on the femora of the posterior pair of legs, and the form of the anal 

 plates. But so similar are these parts in the different groups, that although 

 they distinctly indicate the different genera, it is only by minute peculiarities of 

 their structure that they assist us in identifying the species. The number and 

 form of the dorsal plates at once characterise the Cermatiidce and Lithobiidce. 

 The number of legs and ocelli mark the Scolopendridce. The definite number 

 of joints to the antenna- and the form of the labium indicate the genus Cryp- 

 tops; and the multiplicity of segments to the body and the definite number of 

 joints to the antennae the whole of the Geophilidce. The parts that serve for 

 subdivisions and also for specific descriptions in the extensive genus Scolo- 

 pendra are the denticulations of the labium, the number and character of the 

 spiracles, and of the spines on the posterior pair of legs. 



The dental plates have not heretofore been employed by naturalists in 

 identifying the species of Myriapoda ; but they nevertheless afford good, and 

 the most permanent characters, especially when taken in conjunction with 

 other parts. The denticles on their anterior margin I have called for con- 

 venience, labial teeth. They vary in number and size, and are most distinctly 

 marked, as in Lithobius and Scolopendra, and are sometimes, as in some of 

 the latter genus, themselves armed with other denticuli. In Lithobius and 



