A NEW AND ANNKC'TANT TYPE OF CHILOPOD. 445 



genital orifices in a bivalvular sclerite, representing probably 

 the tergutu of the anal somite^ and by the complete fusion of 

 the sternum and pleura of the fourteenth^ and of the sternum, 

 pleura, and tergum of the fifteenth leg-bearing somites. 

 One family — Craterostigmida^ (Craterostigmusj. 



r d e r 4. — L i t h o b i o m o r p h a. 



Chilopods derivable from the primitive form of Cratero- 

 stigmoraorpha by the excalation of the third, sixth, ninth, 

 eleventh, and seventeenth tergal phites, which brings the terga 

 and sterna into numerical conformity ; by the differentiation of 

 the terga into major and minor in the interests of flexibility ; 

 by an increase in the size of the basal segment of the legs, 

 especially of the posterior pairs, and the segmentation of the 

 tarsi of all the legs, or at least of the thirteenth and four- 

 teenth pairs, to subserve rapidity of movement. In other 

 respects the members of this order stand nearer the primitive 

 type of the Chilopods than those hitherto considered. The 

 tergum of the first pedigerous somite is relatively small in 

 correlation with the weak muscularity of the toxicognaths, 

 the basal segments of which are less strongly fused ; the 

 gonopods, present and jointed in both sexes in more 

 archaic types, are always well developed in the females, and 

 are supported upon a large ventral plate, which results from 

 the fusion of their basal segments with the sternum of the 

 genital somite; and lastly, in two families, the Henicopidas 

 and Cermatobiidto, the stigmata are preserved upon the 

 somite that bears the first pair of legs. 



Three families — Lithobiida) (Lithobius, etc.), Henico- 

 pida3 (Henicops, etc.), Cermatobiida3 (Cermatobius). 



Sub-class Notostigma. 



Chilopods descended from the Cermatobioid type of Litho- 

 biomorpha by the replacement of the normal tracheal system 

 by a series of median dorsal pulmonary sacs furnished with 

 tubes dipping into the pericardial space, and opening each 



