Structure and Affinities of Euphoberia. 441 



plate than at the posterior ; and this place is occupied by a pair 

 of peculiar organs, situated one on either side of the median line 

 at the very front edge of every ventral plate. These, I think, 

 may be supports for branchia3 ; they consist of little triangular 

 cups or craters, projecting outward from the under surface, 

 through which the branchial appendages protruded. Until 

 recently no other organs than branchiae had been found in 

 any arthropod, situated within the legs, and repeated on seg- 

 ment after segment. The only exceptions known are Peri- 

 patus^ a strange creature, allied certainly to the myriopods, 

 but of lower organization, in which Balfour has found seg- 

 mental organs (heretofore known only in worms) having their 

 external openings somewhat similarly situated, and Scolopen- 

 drella, a minute chilopodous myi-iopod, in which Ryder has 

 just described organs which he calls tracheae, opening exter- 

 nally between the legs. But as branchige also occur together 

 ivith sph-acles in some low-organized insects, and then in 

 essentially similar relative positions to that in which they are 

 liere found, and as the possession of legs adapted to swim- 

 ming leads us to presume in these creatures an aquatic or 

 amphibious life, it would seem as if we might fairly conceive 

 these crateriform appendages to be branchial supports*, and 

 conclude that we are dealing with a type of myriopods very 

 different from any existing forms — suited to an amphibious 

 life, capable of moving and breathing both on land and in 

 water. Moreover the assemblage of forms discovered in the 

 Mazon-Creek beds lends force to this proposition ; for the 

 prevalence of aquatic Crustacea, of fishes, and ferns indi- 

 cates that the fauna and flora were those of a region abounding 

 in low and boggy land and pools j and the presence of marsh- 

 frequenting flying insects does not contradict such a belief. 



These, however, are not the only points in which the 

 ancient forms difl'ered from the recent. We have so far ex- 

 amined only a typical segment ; let us now look at the body 

 as a whole and at special segments. The modern Diplopoda 

 are of uniform size throughout, tapering only at the extreme 

 tips ; while these ancient forms, at least when seen from above, 

 diminish noticeably in size towards either end, and especially 

 towards the tail, giving the body a fusiform appearance, its 

 largest part being in the neighbourhood of the seventh to the 

 tenth body-segments, which were often two, or even three, 

 times broader than the hinder extremity, and considerably 

 broader than the head or the first segment behind it. A single 

 segment seems to have carried all the appendages related to 



* Even if they were segmental organs, they may still have been con- 

 nected with respiration. 



