146 ' S. H. SCUDDER ON SPINED MYRIAPODS 



the posterior ventral plate ; they are together equal in length to any part of the dorsal 

 plate, the rings of which the body is composed being equal ; while in modern Diplopoda 

 the dorsal portion of the dorsal plate is always considerably longer than the ventral por- 

 tion, allowing the creature to coil ventrally without exposing any intersegmental portion 

 of the back devoid of hard armature ; while in these ancient forms, the animal appears to 

 coil dorsally as readily as ventrally ; at least, when not extended straight upon the stones 

 in which they are preserved, they are as frequently found bent upward as downward — or 

 perhaps more frequently ; and there is nothing certainly in their structure to prevent it. 

 Indeed in one species, E. flabellata, the ventral plates seem to be divided on either side 

 in the middle, apparently allowing of even greater flexibility, which the arrangement of 

 the posterior dorsal plates for a terminal flap, apparently for aquatic propulsion, would per- 

 haps require in an unusual degree. Then the legs, instead of being inserted at the 

 extreme posterior edge of the plate, originate from almost its very centre, an'd are indeed 

 so large that they nearly occupy the whole of it, a thin lamina only being left at the pos- 

 terior edge of the coxal cavities, though a wider space remains in front ; neither are they 

 inserted close together, but are removed from one another by a space equal to their own 

 width, so that they have ample play (Fig. 3). The legs themselves (see PI. 11, fig. 11) differ 

 from those of modern types in having the second joint as long as the others combined, 

 and the whole leg as long as the diameter of the body, sometimes nearly twice as long ; 

 moreover they are not cylindrical but compressed and slightly expanded, strengthened also 

 on the flattened surface by longitudinal ridges, and have in every respect the aspect of 

 swimming legs in those specimens in which the appearance of the legs is most clear. No 

 modern aquatic myriapods are known. The spiracles, instead of being minute and hav- 

 ing the position seen in modern Diplopoda, are very large, situated in the middle of each 

 ventral plate (Fig. 4), 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, i. e. across the body ; its length equals the diameter of the large 

 coxal cavities. 



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

 ventral plates in modern Diplopoda, we find in these ancient types some further interest- 

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

 their presence and their adherence to the ventral plates. The coxal cavities are not cir- 

 cular but oval and are situated with the major axis in an oblique line, running from near 

 the middle line of the body forward and outward ; this, and the slight posterior insertion of 

 the legs leave even a wider space between them on the anterior edge of the plates than 

 posteriorly, and this place is occupied by a pair of peculiar organs (see Fig. 3 and PL 11, 

 figs. 1-4), situated one on either side of the median line at the very front edge of the ven- 

 tral plate ; to these it seems to be impossible to assign any other function than that of sup- 

 ports for branchiae ; they consist of little triangular cups or craters projecting from the 

 under surface, through which I believe the branchial appendages protruded ; so far as I am 

 aware, no other organs than branchiae have been found in any Arthropoda situated within 

 the legs, and repeated on segment after segment; a single exception may perhaps be 

 made of Peripatus, in which Balfour has found segmental organs having their external 

 openings somewhat similarly situated ; but this being the only known instance of their 



