THE OLDEST AIR-BREATHERS. 



397 



formation, the appendices belonging to which resemble those found 

 in the scorpions of our own day." This species has been named Palce- 

 ophoneus nuncius. 



The Scottish specimen (Fig. 2) is described by Mr. Peach in " Na- 

 ture " as being about an inch and a half long, and lying on its back 



on the stone. " Its exposed ventral surface shows almost every ex- 

 ternal organ that can be seen in that position, and in this way serves 

 to supplement the evidence supplied by the Swedish specimen. As in 

 the northern individual, the first and second pair of appendages of the 



