236 THE ORIGIN OF VERTEBRATES 



of these forms, for they possess only five free prosomatic appendages 

 instead of six, as in Limulus and in Pterygotus. Similarly, Wood- 

 ward only allowed five appendages for Pterygotus, so that his restora- 

 tions were throughout consistent. Schmidt, in Pterygotus osiliensis 

 has shown that the true number was six, not five, as seen in his 

 restoration given in Fig. 8, A (p. 27). 



With respect to Eurypterus, Schmidt figures an exceedingly 



Fig. 103. — Ventral Surface op Limulus. (Taken from Kishinouye.) 



The gnathic bases of the appendages have been separated from those of the other 

 side to show the promesosternite or endostoma (End.). 



minute pair of antennae between the coxal joints of the first pair of 

 appendages, thus making six pairs of appendages. Gerhard Holm, 

 however, in his recent beautiful preparations from Schmidt's specimens 

 and others collected at Bootzikiill, has proved most conclusively that 

 the chelicera3 of Eurypterus were of the same kind as those of 

 Limulus. I reproduce his figure (Fig. 104) showing the small chelate 

 chelicerce (1) overhanging the mouth orifice, just as in Limulus or in 

 Scorpio. 



