THE EURYPTERIDA OF NEW YORK 217 
also short and thick. The surface of the carapace exhibits in front an 
unusual sculpture consisting of intricately mingled short, coarse, curved 
ridges of confluent tubercles. On the posterior part of the carapace the 
tubercles are mostly separated. The axial knots on the segments were 
solid bodies. All these features combined demonstrate that the integument 
of this subgenus was not merely chitinous as in the typical Eurypterus, 
but much strengthened by calcareous deposits which became most promi- 
nent in the sculpture of the carapace and in the knots of the tergites. 
This thickening of the carapace 
is entirely in accord with the char- 
acter of the Guelph fauna described 
by the authors from New York, 
where the fact of the peculiar thick- 
ening of the shells in all classes, 
notably the brachiopods and mol- 
lusks, has been emphasized and 
been ascribed to the strongly saline 
water and in part to the life of the 
organisms on wave-beaten coral 
Figure 42 Tylopterus boylei (Whiteaves). 
Holotype refigured in natural size, and enlarge- 
ment of sculpture of carapace 
reefs. Tylopterus boylei 
seems to be an adaptation to the 
same peculiar conditions which are also indicated by the character of 
the matrix of the fossil, a porous, coarse-grained dolomite. 
It would suggest itself to compare this species with the Carbonic 
eurypterids described by Etheridge (E.? stevensoni, see text 
fig. 48) and Woodward (E. scabrosus) in which the integument 
has become greatly thickened by deposition of globular calcite (“ cal- 
culi”’).” We have in another place considered these features as phylo- 
gerontic in the Carbonic subgenus Anthraconectes and as due to the waning 
vitality of the race. It is hardly to be assumed that the characters of 
the Siluric T. boylei are due to the same gerontic conditions and 
that the latter is an ancestor of the Carbonic Anthraconectes. It would 
