184 
I am not myself in the case to be able to undertake a 
grouping, not having representatives for more than half 
of the genera; I mean, however, to be able to point out 
several new structural features of systematic value. 
These are: 1) occurrence and structure of the stridulating 
apparatus, 2) structure of the basis of tarsus of the 3 
pairs of ambulatory limbs, 3) shape of the rostrum, 
4) size of the anal aperture; in the following they are 
separately described. 
E. Stridulating Apparatus. 
A large portion of the interior side of the mandible 
is, as well known, taken up by anaked, shining, square 
plane, being mostly a little shorter, sometimes (Cleobis) 
as. long as high, the anterior margin of which is. 
curved a little backwards at the middle. In Solpuga 
fatalis Licht. (Tab. II, fig. 8) sharp keels, about 12 
in number and turning backwards, issue from the upper- 
most 2/; of this anterior margin, the top one but three 
of which is the longest, and from thence they decrease 
in length both upwards and downwards; the inferior 
ones becoming thus very short. Some very short 
keels are seen in the bottom of the rather deep furrows 
near the anterior margin. This structure is uniform on 
both mandibles and in both sexes. — I took a very 
large specimen of S. fatalis, placed my fingers on the 
centre of the exterior side of the mandibles, pressed 
them against each other and moved them in this way 
alternately up and down in the vertical plane, just as 
the animal must be able to move them; the result was 
that the 2 furrowed parts of the 2 inner sur- 
faces rubbed against each other and produced 
a sound that could be heard in a room ata 
distance of more than 3 metres. Though I do 
