216 NEW YORK STATE MUSEUM 
The fourth specimen is very fragmentary, poorly preserved and 
recognizable as belonging here only by the presence of the terminal spines 
of the paddles. / 
E.kokomoensis bears some similarity to E. remipes in 
the squarish outline of its carapace and the proportions of the carapaces 
and preabdomina. It was not so well adapted to swimming as is 
shown by the less developed and more slender swimming legs and the | 
presence of a terminal spine, obviously used in walking, and also by the 
shorter and stouter postabdomen. While the species may have been a 
less active swimmer, the extremely broad doublure of the carapace may 
indicate an adaptation of the front edge to shoveling or digging. 
Subgenus TYLOPTERUS ! nov. 
This subgenus is proposed for the species, Eurypterus boylei, 
described by Whiteaves from the Guelph formation of Ontario; a form 
which exhibits a number of characters that show it to be an aberrant type 
distinctly adapted to the peculiar conditions of the Guelph sea. ‘These 
special traits are found in the thick integument of carapace and abdomen 
which apparently was not only chitinous but calcareo-chitinous; the highly 
raised lateral margins of the carapace and the presence of elevated and 
divided knots on the second to fifth tergites. 
The extraordinary thickness of the test is shown not alone in the 
wholly uncompressed condition of the carapace but more 1n the fact that, 
though the abdomen has been shoved forward so that the segments are 
pushed into each other like joints of a telescope, they have not suffered 
from crumbling or folding as they always do in the other eurypterids and 
their greatly thickened posterior edges stand out freely. The front margin 
of the carapace forms a broad beveled shoveling edge, while the lateral 
margins are much thickened and elevated into prominent ridges. The 
abdomen seems to have been very compact and short, as shown by the 
relatively short last two postabdominal segments. The telson spine is 
‘rvAn, knot; mrepov, wing. 
