The Craspedosomatidae of North America. 29 



C Length 6-9 mm F 



} 14-25 mm G 



( Setae long ; carinse large ; segments 28 Tricliopetalum 



I short; carinse small; segments 30 H 



( Carinse large; body outline serrate Coiiotyla 



I inconspicuous or wanting I 



( Ocelli 27; carinse rounded Bactropus 



I 13; carinse striseform Underwoodia 



^ Sixth and seventh antennal joints equal, slender Cleidogoiia 



I twice as long as seventh, stout ; body striate Caseya 



To judge from the works of Latzel, Haase and Yerhoeff, thei-e 

 ^re also among the European Craspedosomatidae groups of species 

 :agreeing in secondary sexual characters, but there seems to have 

 been no attempt at an arrangement based on homologies of this 

 «ort. We notice after the descriptions of the American forms 

 the more striking of this class of characters as exhibited in the 

 European genera and species, the generic descriptions being ar- 

 ranged on lines parallel with those previously given. 



Dr. John A. Ryder was the first to use such characters as 

 •a basis of generic distinction. In describing Zygonopns he calls 

 attention to the recognized importance of sexual characters in 

 the generic classification of other groups, notably Crustacea, and 

 nfflrms their availability in the Myriapoda. 



In the Polydesmidse the ninth male legs are unmodified, while in 

 Craspedosomatidae we have a series of gradations from the five- 

 jointed down to a nearly or quite complete transformation into com- 

 plex genital apparatus. In America are found the first members of 

 the series, from five-jointed to two-jointed, while the others are 

 found in Europe. It may be that in the European forms these 

 legs have so completely taken on the function of genitalia as to 

 be more susceptible of specific modification and are not of so 

 much value in generic distinction ; in the American forms, at 

 least, the}' seem worthj^ of all the weight given to rudimentary 

 and secondary sexual characters. Among the species, already 

 known the form of the ninth male legs is so constant an index of 

 ■a whole complex of characters of other kinds that it is possible to 

 distinguish the genera by them alone, as in the following table: — 



( Ninth male legs 4- or 5-jointed B 



( 2- j ointed C 



{ First and second Joints thick, subequalin size Cleidogona 



I very large, the second cylindrical, slender D 



