440 Mr. S. H. Scuclder on the 



plates occupy the entire ventral surface, perhaps may be said 

 to extend partly up the sides of the rounded body ; and no part 

 of the dorsal plate passes behind the posterior ventral plate. 

 They are together equal in length to any part of the dorsal 

 plate, the segments of the body being equal in length through- 

 out ; while in modern Diplopoda the upper portion of the 

 dorsal plate is always considerably longer than the ventral 

 portion, allowing the creature to coil ventrally without expo- 

 sing any intersegmental portion of the back devoid of hard 

 armature : in these ancient forms the animal appears to coil 

 dorsally as readily as ventrally ; at least, when not ex- 

 tended straight upon the stones in which they are preserved, 

 tliey are as frequently found bent upward as downward ; and 

 tliere is certainly nothing in their structure to prevent such 

 mobility. 



Then the legs, instead of being inserted at the extreme 

 posterior edge of the plate, are planted almost in its very 

 centre, and are indeed so large that they occupy nearly its 

 entire width ; neither are those of opposite sides inserted close 

 together, but are removed from one another by a space equal 

 to their own width, giving them ample play. The legs them- 

 selves differ from those of modern types in having the second 

 joint as long as the others combined, and the whole leg at 

 least as long as the diameter of the body, and sometimes nearly 

 twice as long ; moreover they are not cylindrical but com- 

 pressed and slightly expanded, strengthened also on the flat- 

 tened surface by longitudinal carinfe, and in every respect, in 

 those specimens in which the legs are best preserved, have 

 the aspect of swimming-organs. No aquatic forms are known 

 among recent myriopods. 



The stigmata, instead of having the position they hold in 

 modern Diplopoda, where they are necessarily minute, are 

 very large, situated in the middle of each ventral plate, each 

 spiracle opposite to and indeed touching the outside of the 

 coxal cavity of the plate to which it belongs, and running 

 therefore with and not athwart the plate, t. e. across the body. 

 But in addition to these structures, which make up the sum 

 of the furniture of the ventral plate in modern Diplopoda, we 

 lind in these ancient myriopods some further interesting- 

 organs, which are so perfectly preserved that no doubt can be 

 entertained concerning their presence and their adherence to 

 the ventral plate. The coxal cavities are not circular but oval, 

 and are situated with tlie major axis in an oblique line, run- 

 ning from near the middle line of the body forward and out- 

 ward : this and the slight posterior insertion of the legs leave 

 even a wider space between them at the anterior border of the 



