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 
Fic. 103.—VENTRAL SURFACE OF 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 (Hnd.). 
minute pair of antenne 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 Rootzikiill, has proved most conclusively that 
the chelicere of Eurypterus were of the same kind as those of 
Limulus. I reproduce his figure (Fig. 104) showing the small chelate 
chelicerz (1) overhanging the mouth orifice, just as in Limulus or in 
Scorpio. 
