THE EURYPTERIDA OF NEW YORK 247 
The specimen measures 24 inches in length, whereas none of those 
from which the description of C. newlini was compiled exceeded 
14. There are also only three cusps on the front edge of the first, third and 
fourth pairs of gnathopods, and four on the second pair. In C. new- 
lini these cusps are sometimes 8 to 12 in number, and apparently in 
some cases project from the back of that organ, though this must be con- 
sidered uncertain and against analogy. 
There is, moreover, on the large paddles, no trace of the fringed or 
serrated edges which are so conspicuous in the paddles of C. newlini. 
They are perfectly even and smooth. 
None of the differences cited seem to us to warrant any specific distinc- 
tion, the different size being clearly due to age, since no important corres- 
ponding discrepancies in the proportional lengths of the parts of the body 
could be found to corroborate the supposed distinction. The cusps are, 
to our knowledge, of like number in all these Eusarci, all segments, save 
the first two and the last, bearing two spines each, the last forming a single 
spine. Both spines were of nearly equal size, as we have already ob- 
served in the generic description, but frequently only those of one side 
are observable, the others being either broken away, leaving their wartlike 
bases [pl. 33, fig. 1], or imbedded in the rock above or below the bedding 
plane on which the body rests. Of the two specimens of Eusarcus 
newlini before us, one [pl. 37] shows the spines of both sides and would 
hence correspond to E. newlini s. str., the other only those of one 
side and would hence have in this regard the character of E. ingens. 
The last difference cited is the absence in C. ingens of the fringed 
or serrated edges “‘so conspicuous in the paddles of C. ne wlini.’’ Much 
of the serrated appearance of the edges of the paddles in the eurypterids 
is due to a cracking of the thickened margin of this thin leaflike organ. 
For this reason one frequently sees in some specimens of this species an 
apparently very marked serration, while others have a distinctly smooth 
edge. The same is true of both E. newlini and E. ingens, 
E.newlini possessing, in reality but a very weakly developed serration. 
_ The supposed differences between E. newlini and E. ingens 
are doubtless due to slight variations in preservation, but even if of actual 
