II2 NEW YORK STATE MUSEUM 
p. 198] makes a positive statement that the Carbonic Eurypterus 
scouleri is a fresh-water form, basing his conclusion on the character 
of the rocks and the associated flora and fauna. | 
There seems hence little doubt that the eurypterids of the Carbonic 
finally abandoned the sea and entered the fresh water. Directly thereafter, 
in the Permic they became extinct, the last of the race being the Euryp- . 
terus douvillei de Lima, found in the Rotliegende of Portugal 
associated with Walchia pinniformis and Sphenophyl- 
lum thorn. 
Summarizing these data we conclude that the eurypterids lived in the 
sea from Cambric to Siluric time. They had then become less sensitive 
to changes, positive and negative, in the salinity of the water. In fact 
they seem to have thrived best under conditions of life that exclude most 
other marine groups of animals, that is, in the marginal, more or less 
inclosed marine lagoons, accompanied by estuaries receiving delta-forming 
terrestrial drainage, with prevailing arid or subarid climate, the waters 
being in some places more than normally briny, in others having less than 
normal salinity. In other words they were euryhaline or able to live in 
both salt and. brackish water. 
Their adaptation to such conditions is paralleled today by such crus- 
taceans as Apus and Artemia which not only thrive under rapid diminution 
of normal salinity but, by means of strongly protected eggs, even survive 
salt pan conditions which end in complete desiccation, as shown by their 
well known occurrence in desert lakes. The usual associates of the Siluric 
eurypterids are peculiar crustaceans whose nature emphasizes the reference 
above made. They are phyllocarids and ostracods and members of the 
strange family Hemiaspidae (Neolimulus, Bunodes, Hemiaspis, Pseudonis- 
cus). This congeries of peculiar crustaceans seems to constitute a fauna 
especially adapted to, and therefore highly characteristic of, lagoon ,and 
estuary conditions. 
Thus while the earlier eurypterids were marine and their climacteric. 
fauna euryhaline; their later habit throughout the Devonic and Carbonic 
‘led them finally into the fresh water. 
