730 
PALEONTOLOGY: C. SCHUCHERT 
over, the illustrations of the Mississippi delta in our text-books are on 
so small a scale as to give an erroneous conclusion as to the amount of 
Ithe river flood-plain area. A large-scale map shows that 50% or even 
more of this delta is under the waters of the Gulf of Mexico, and in 
areas like Lakes Ponchartrain and Borgne the largest of eurypterids 
may have dwelt. Hence it will always be very difhcult to separate 
the deposits of such areas, with their mixed biotas, from those of the 
river flood-plains on the one side, and on the other from those of the 
more or less marine bays. 
In this connection we should not neglect to state that nearly all the 
eurypterids occur in strata of times when the continents were largest 
and when the rivers were rejuvenated to stronger and longer flow into 
the interior seas. Also that Eurypterus lived from Ordovician into 
Permian time, and Pterygotus was distributed almost throughout the 
world during the Siluro-Devonian. However, at the times when the 
seas have their greatest spread we find almost no merostomes of any 
kind. These are significant facts bearing upon the probable habitats 
of the Paleozoic merostomes. 
Since it appears that the eurypterids are probably in the main fresh- 
water animals, and as some of them take on the form of scorpions and 
may therefore be spoken of as river scorpions, this admission opens a 
most wonderful vista into the probable life of the land during early 
Paleozoic times, as far back at least as the Upper Cambrian. There 
are other merostomes of the order Limulava (two genera) in the Middle 
and Lower Cambrian, and these antennate forms are more directly 
related to the eurypterids. Of the Synxiphosura, forms ancestral to 
the Xiphosura, the Middle and Upper Cambrian have at least four 
genera. As all of these animals also appear to have lived in fresh water, 
it would seem that the rivers of Cambrian time were peopled by mero- 
stomes none of which exceeded 6 inches in length, but in late Silurian 
time they were not only far more varied in form, but Pterygotus at 
least, the most active and predaceous of them all, attained a length 
estimated at from 6 to 9 feet. Stylonurus, the great spider-Hke euryp- 
terid of the Devonian rivers, may have attained a similar length. In 
regard to these and other eurypterids, Clarke and Ruedemann,^ the 
authorities on these arthropods, think that most of our museum speci- 
mens are immature individuals, and often the casts of tests, conditions 
further favoring the theory that they are fresh-water animals whose 
thin, light tests were easily drifted by the rivers into the estuaries and 
the seas. The considerable variety and the great size attained by some 
forms means that there was an abundance of food, both animals and 
