322 NEW YORK STATE MUSEUM 
oblong scales that rise rapidly behind and suggest raindrops running 
down a windowpane [pl. 58, figs. 1, 2], with a row of especially large 
drops at the bottom, on the posterior margin of the segments. This pecu- 
liar ornamentation is also best developed in species of Stylonurus, though 
it also occurs in some of the later, especially the Carbonic, species of 
Eurypterus. 
Both the extreme spinosity of the endognathite and the surface sculp- 
ture indicate that Echinognathus, in comparison to Strabops or Eurypterus, 
was already a highly specialized genus and was either closely related to 
Stylonurus or had a convergent development to that genus as far as the 
two characters mentioned are concerned. There are no other characters 
observable in the fragments that would appear competent to shed light 
on its generic relations. 
The monotype of this genus 1s 
Echinognathus clevelandi Walcott 
Plate 58, figures 1, 2 
Eurypterus? clevelandi Walcott. American Journal of Science. 1882. 
23:152. figs. I, 2 
Echinognathus clevelandi Walcott. Idem. p. 213 
q 
We reproduce the original description as follows: 
The only portion of the body discovered is illustrated by figure I. 
It appears to be the left side or half of the ventral surface of the anterior 
thoracic segment. The reference to the ventral surface is from the presence 
of a thin membranous extension of the anterior margin, a feature observed 
on the anterior segment of Dolichopterus macrochirus Hall.! 
The test appears to have been thin and firm, and the margins are clearly 
outlined on the dark, smooth slate, while the surface is ornamented with 
fine scalelike markings on the anterior portion that increase in size toward 
the posterior margin (cc). 
Figure 2 1s a sketch, seven tenths of the natural size, of the cephalic 
appendage as it appears on the surface of the slate and in the matrix. The 
entire length of the appendage from the point aa to the end of the terminal 
1 Palaeontology of New York, 3:414*.' 
