S. W. Ford—Additional Embryonic Forms of Trilobites, 255 
life. It is earnestly to be hoped that pars British and Swedish 
savans will institute, at no distant da w researches, with the 
view of reaching a clear and final pi i of this important 
question. 
But by far the most interesting feature of the young speci- 
men of Olenellus asaphoides first described yet remains to be 
particularly considered. I allude to the remarkable Paradoz- 
ry. Pe run of the outer portion of the posterior margin of the 
, Shown at aa in figure 1. This feature, though nee We 
section; but i n in none of the other species of th 
genus Olenelius, and even disappears altogether, as we have 
seen, in O. oc ean during embryonic life. After much 
may be vapuilels as fixed. It is e, that in O, Gilber nee the 
posterior margin is deeply sinavpreats in the vicinity of the 
postero- -lateral ; angles; and this feature, as shown by the figures 
the facts, will be likely to reach a different ae The 
discovery, however, of still younger specimens of O. (ilberti is 
greatly to be de sired, as they would doubtless serve to throw 
much light upon the ‘whole question. 
Now, if the foregoing interpretations be correct, Olenellus 
asaphoides must be regarded as higher in grade than any of the 
normal species of Paradoxides ; and such I believe its history 
and structure alike declare it to be. The following additional 
facts and si peck appear to me to sustain this conclusion, 
and tend to clear up a number of points hitherto obscure con- 
oe with the nate sek 
10 represents the plan of structure of the head of a 
Swedich Paradoxides, described by J. G. O. Linnarsson, in 
1871, under the name of P. Ajeru/fi.t The thorax in none of 
the examples figured is well nda but from the study of 
White, Rep. upon ngeik and Geol. Pir asl - apts PpSs las the One Hun- 
dredth Meridian. Part I, vol. i v, Paleontology, p. 4 gs. 3 
+ Oefve ersigt a ‘Votnutage Avademians ig i Sa a ine No 6 6, Stockholm. 
