THE EURYPTERIDA OF NEW YORK 375 
sons. As no entire specimen has been obtained, we are not in position to 
say whether all these parts belong to but one or to several species. We 
have referred them provisionally to one species since the carapaces do 
not exhibit differences of sufficient importance to base distinctions upon, 
though they undoubtedly represent different growth stages. We have 
selected the largest and most perfect carapace [pl. 82, fig. 6] as the type 
and derive from ‘this the following description: 
Description. Carapace approaching a circle in outline, with a pos- 
terior segment cut off, so that the length is one fifth shorter than the 
width. The greatest width is in the anterior half, just behind the eyes. 
The frontal margin and the greater portion of the lateral margins form 
a continuous subcircular curve, the posterior fourth of the lateral margins 
slightly concave and the posterior margin nearly straight. The post- 
lateral angles are approximately right ones. A narrow flat margin with 
a thickéned rim surrounds the carapace except where the eyes are situated 
where it is presumably continuous and turned under. This margin 
widens near the postlateral angles. The posterior margin is also fur- 
nished with a narrow flat border. The carapace appears to have been 
quite convex before compression. The eyes are very large (one half the 
length of the carapace), of elliptic outline, hardly projecting, and situated 
at the well-rounded antelateral corners. Traces of the facets are notice- 
able. The surface is ornamented with contiguous, low broad tubercles. 
The first tergite is very short (11 times as wide as long), its posterior 
margin concave in the middle, the lateral margins rapidly diverging and 
curved. The surface exhibits the same ornamentation as the carapace. 
several tergites have been observed of a Pterygotus exhibiting the 
same typical Pterygotus-sculpturing as the carapace of this species, though 
more pronounced. One of these, with much extended lateral “ ears ”’ 
is reproduced on plate 82, figure 8. Some fragments indicate that this 
Species attained the gigantic proportions of the Bertie waterlime species 
and that the smaller forms are but early growth stages. The relatively 
very great size of the lateral eyes points to the same conclusion. 
