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THE POPULAR SCIENCE MONTHLY 



But on the whole, we felt that the results of our European expedi- 

 tion were incomplete, because nothing like a full account of the gross 



anatomy of any one species of ostra- 

 coderms was obtained. The organs 

 about the mouth and the location 

 of the principal viscera and of the 

 nervous system were entirely un- 

 known ; and it was quite essential to 

 obtain evidence on these points, 

 because it had become increasingly 

 clear that this strange class of ani- 

 mals could not be safely interpreted 

 in terms of either vertebrate or in- 

 vertebrate anatomy. 



On my return to America it 

 was decided to make an attack on 

 a younger branch of the ostraco- 

 derms; one that was known to 

 occur in the Devonian rocks of the 

 Bay of Chaleur in Canada. 



Four summers were spent in 

 this locality, in search of specimens 

 well enough preserved to be used 



Fig. o. Restoration op Tremataspis, for anatomical study. Fragments, 

 an Ostracoderni from the upper Silurian . , ., . , 



rocks of the Island of Oesel, Baltic Sea. 0r m some cases nearl y the whole 



head, could be readily found on the 

 beach at low tide, or by splitting open the disc-shaped nodules that 

 had been washed from the adjacent cliff. But these specimens were 

 generally crushed out of shape, or were so badly weatherbeaten and 

 worn that they were of little value. We hoped to find in the cliff, 

 which extended along the water front for several miles, unweathered 

 specimens that would show not only the whole head, but the rest of the 

 body, the nature of which at that time was entirely unknown. We 

 accordingly examined with great care the face of the cliff as far as it 

 was accessible ; and many tons of rock were dug out of it and split open 

 in order to locate the particular beds that contained the fossils ; but the 

 latter appeared to be very irregularly distributed, for we did not suc- 

 ceed in finding a single specimen in that way. 



At last we found, close to the foot of the cliffs, a large piece of rock 

 that contained several fossils of the kind we were looking for. It could 

 not have been carried there either by the waves or by drifting ice, for 

 evidently it had fallen quite recently from the rocks above. It did not 

 take long to locate, about twenty-five feet above this fragment, the beds 



