PALEONTOLOGY OF NEW YORK. 



untero-lateral the margin is strongly thickened, on the postero-lateral 



roadly infolded, and its thickened edge continuous with the 

 or .-pine. This ridge on the doublure is distinctly marked upon the 

 surface of the carapace when compressed. 



_ lit 1 \- convex and bears a strong, somewhat elongate 

 ■ le, situated just in front of the extremity of the lateral carina, and 

 toward the dorsal line. The summit of this optic node bears a deep pit or 

 invagination, which may have held a lense or series of lenses, or it may be 

 of a more embryonic character in the visual organs. Upon the 

 thoracis n is a strong, straight carina, extending its entire length. Its 



sides are broadly sloping, and well-preserved individuals show a finely incised 

 longitudinal line about half way up each slope. On the inner slope, be- 

 tween this line and the summit of the ridge, there is a series of oblique 

 crenulations. 



The S is ornamented by a number of low tubercles in the inter-ocu- 



;on, and elsewhere over the cephalic area by fine, elevated, frequently 



tnosing lines; upon the extra-carinal area these lines become longer 



and more continuous. Otherwise the surface is minutely punctate or 



iomeh composed of two somites of which the anterior was probably almost 



aled beneath the carapace. This somite is short, one-half as long as 



ind slightly elevated at the margins into articulating ridges; the 



somite is quadrate and somewhat longer than wide. The sur- 



s ornamented by strong, elevated, venate lines, which, 



terior joint, radiate from the crenulated margins and are directed 



'"' upon the posterior they also radiate from the margins but are 



"Wd and backward. In one specimen these lines are crossed by 



I wrinkle, which appear to be due to compression. 



•r somite bears a few low, broad tubercles. 



dal plate sub-triangular on the ventral surface, distinctly 

 the anterior extremity lor articulation with the last somite; sub- 



