254 S. W. Ford—Additional Embryonic Forms of Trilobites. 
canon in Natural History, O. asaphoides must be regarded as 
higher in grade than its macropleural congeners; and_ this 
. being true, we are naturally led to inquire whether the brachy- 
pleural forms under the genus Paradozxides are not also higher 
in grade than their macropleural congeners. Unfortunately, 
the direct evidence required to decide this question is wanting ; 
ut there are certain known facts having an important bearing 
upon it, and to these I shall now refer. 
Fig. 7.—Head and first 8 body-segments of adult specimens of Paradowides 
spinosus (macropleural), reduced two-thirds. Compare with fig.4. Fig. 8—Head 
and 9 forward pleura of adult of P. Tessini Brongn. (brachypleural), reduced 
one-half (after Angelin). 
Among the macropleural Paradoxides described by Barrande, 
there are a number of species of which we lack either one or 
species. Nevertheless, it is not difficult to see that such a 
result might easily have been attained; and from what we now 
know of the history of O. asaphoides, coupled with the facts 
just stated, there is strong presumptive evidence that the 
brachypleural species of Paradoxides were macropleural in early 
