THE GENEIU AND SPECIES OF SYMPHYLA. 25 



Scutigerella are clothed with a larger number of hairs than 

 those of the other genus; furthermore, the sette on the 

 antennae are longer, the branched sense-organs on the last 

 antennal joint are much larger, the central rod in the head is 

 anteriorly less developed and often partly inconspicuous, 

 while it is well developed in Scolopendrelhi, the fine and 

 short hairs on the legs are somewhat longer and more con- 

 spicuous than in the last-named genus. The species of 

 Scutigerella generally acquire a more considerable length 

 than those of Scolopendrella. On the geographical distribu- 

 tion of the genera see above on pp. 21, 22. 



Gen. 1. Scutigerella, Ryder. 



Conspectus op the Species. 



It may be practical first to divide the species into three 

 sharply defined groups, and then to give a conspectus of the 

 species of each group. 



A. The last dorsal scutum posteriorly with a very deep 

 and rather large median, anteriorly overlapped cavity. The 

 second scutum with the antero-lateral sette directed essen- 

 tially backwards and much shorter than the breadth of the 

 proximal antennal joint . . . Group I. 



B. The last dorsal scutum posteriorly cut off without any 

 median cavity, at most with a simple depression. The 

 second scutum with the antero-lateral seta; directed straight 

 outwards or even somewhat forwards, and at least nearly as 

 long as the breadth of the proximal antennal joint. 



a. The setse on the inner side of the proximal antennal 

 joints directed obliquely forwards, and, at most, nearly one 

 half longer than the sette on the outer side. The exopods of 

 the posterior legs well developed, as long as or longer than 

 the depth of the tarsi. The last scutum slightly depressed 

 posteriorly along the middle . . Group II. 



h. Some setae on the proximal antennal joints nearly 

 vertical to the lono'itudinal axis of the antennae and besides 



