THE HORSE FOOT CRAB. 211 
The above fact was obtained by evidence purely negative, 
yet not the less convincing. First, there was the suspicion of 
the fact, then the search for a young male possessing nuptial 
claws. But albeit the numerical equality of the sexes this 
was not found, though large numbers of young specimens of 
different ages were examined. Moreover, I have not found 
the fisherman who has ever seen one. 
Although some of the systematists make of Limulus a 
distinct order, as Xiphosura, or sword-tailed ; yet I cannot 
but think that in nature the Trilobites are included, making 
of all one grand order. It would thus have not only a real 
systematic meaning, but a profound chronologic significance. 
However this may be in the light of coming knowledge, I 
think Pterygotus and Eurypterus stand higher than the typi- 
cal Trilobite proper, and that Limulus leads rank over all. 
Figure 68 shows Limulus after the first moult (very 
much enlarged), when not more than a week old. The 
fringe of the buckler is now less thickly Fig. 68 
set, the cardinal spines only being con- 
served, and these not so stout. The 
posterior shield shows the permanent 
spines. Still the contour is asaphoidal 
while the median ridge of the abdom- 
inal carapace, terminating in the point 
of the mucronated shield, is suggestive 
of the dorsal keel in Pterygotus gigas e 
and P. anglicus. At this stage, as the  Limulue after the rst mouit. 
facts seem to me, the larval Limulus shows forth more than 
one generie "expression point" in the career of the trilobite 
as a "comprehensive type." 
It should be stated here that thé exuvia represented by 
fig. 68 was accidentally discovered on the surface of the mud, 
at the bottom of an hatching jar, used in these observations 
last summer. At the close of the warm season last year 
my jars must have contained not less than two hundred 
young Limuli. We have already said that so soon as 
