120 PALEONTOLOGY OF NEW YORK. 



spines which reach as far as the fourth segment of the thorax. Posterior 

 margin transverse. Surface moderately convex. 



Facial Sutures normal, approximating on the frontal margin. 



Glabella simple, elongate, sub-conate, sloping to a broadly rounded anterior 

 extremity, which encroaches upon the frontal border. Length one-third 

 -nater than the width. Surface convex, longitudinally arched when nor- 

 mally preserved. There are usually no traces of lateral furrows, but a single 

 individual in which the crust is slightly separated from the rock and has 

 .me translucent, shows evidence of three oblique lines, apparently the 

 second, third and fourth lateral furrows; the first pair being obsolete, and 

 the fourth extending only part way across the glabella. Occipital lobes con- 

 spicuous, transverse; occipital furrow narrow and sharply impressed, scarcely 

 widening upon the cheeks; occipital ring broad, arched and somewhat flat- 

 tened, narrowing slightly to the genal angles. 



Eyes approximate, large, lunate, not elevated above the surface of the 

 glabella; extending from the occipital lobes two-thirds the length of the 

 glabella. Visual surface quite convex, particularly in young individuals. 

 Palpebral lobe moderately large, sloping inward to the palpebral sulcus, 

 which is sharply incised. 



Cheeks relatively narrow on account of the size of the eyes. Conspicu- 

 ously grooved or depressed about the orbital ridge, and rounding more or less 

 abruptly to the margin. The border is unusually wide and carries two paral- 

 lel grooves, the outer of which is narrow and marginal, producing a beveled 

 edge; the inner broad and shallow, becoming flat in old individuals. On the 

 posterior border the margin is also beveled, and the genal spines are strongly 

 ridged by the meeting of these beveled edges. 



Thorax transversely sub-rectangular, lateral margins slightly rounding and 

 approximating posteriorly. Length to width as 2 to 3. Surface convex and 

 strongly trilobate. Composed of ten segments. 



Axis arched, having more than one-third the width of the thorax; widest 

 at the third or fourth segment, and tapering with slightly rounding margins 



