242 A Monograph of Scytonotus. 



indicates that the additional joints are eitlier intercalated between 

 the others or at base, probabl3- the latter, for the second joint of 

 the larval antenna also has some of the finger-like sense-organs, 

 like the fifth joint of the adult. 



There are five pectinate laniellje, the number being constant in 

 the three individuals of which the mandibles were examined. 



The styliform processes of the median lobe of the gnathochilar- 

 ium are much larger proportionately than in the adult, and are 

 tridentate as in Chordeumidae. The cones of the processes of the 

 stipes are ver}^ few. 



The greatest difference between the young and the adult is that 

 the former is covered with clavate, barbed, bristles (fig. 69). 

 Such have been reported as occurring on the embrvo of Strongyl- 

 osoma guerini, but do not seem to have been noticed at a more 

 advanced stage. Both Rath and Packard liaA-e observed the six- 

 legged larva of Pol3'desmus,' and both report the bristles as 

 clavate, but do not mention that they are barbed, though the im- 

 portance of this latter fact would have doubtless been realized 

 on account of the attempt to connect the Arehepoh'poda with 

 the modern Diplopoda by means of the barbed hairs of Polyxenus. 

 On the larval Scytonotus the hairs are more clavate dorsally, 

 on the sides and below becoming more and more of the usual 

 shape. 



The four bristles of the apex of the last segment are also in 

 notable contrast to those of the adult, both in their great size 

 and large pedicels. All the hair-structures of the larva have 

 more or less of a raised base, except those of the legs and 

 antennas. 



The larval claw is distinctl}' bifid, though the inside hamus is 

 very small (fig. 71). In the adult an exceedingly minute rudi- 

 ment of this may be found under a quarter-inch objective. 



The larvoe measure 1.25 mm. in length, and A mm. in width. A 

 considerable number were found together, and they were probably 

 newl}' hatched. 



'Dr. A. S. Packard has reported (American Naturalist, 1886, p. Gol) 



the six-legged larva of Polydesinus canadensis from Florida, as having 



eight segments. We have not seen canadensis from the Soiith. Other 

 similar si)ecies replace it there. 



