60 PALEONTOLOGY OF NEW YORK. 



broader and deeper on the cheeks, occipital ring prominent and bearing short 

 and sharp central spine; narrowing to the axial furrows, thence rapidly 

 u idening to the genal spines. 



Eyes lunate, large and elevated considerably above the summit of the 

 glabella, and closely appressed against its coalescent first and second lobes. 

 Visual surface with numerous corneal lenses, the single specimen (a young 

 individual) in which they may be enumerated, showing eighteen rows, 

 counting diagonally from the lower posterior margin, and one hundred and 

 ninety-two lenses. Palpebrum scarcely prominent; palpebral lobe depressed 

 and sloping abruptly to the narrow and elevated palpebral furrow. 



( 'hecks sloping abruptly from the ocular node to the thickened and some- 

 what flattened margin. A deep sinus, which is stronger in old individuals, 

 hounds the ocular node and flattens the subjacent portion of the cheek. 



Thorax sub-rectangular, length to width as 4 to 5. Surface depressed-convex. 



Axis relatively narrow, widest at about the fifth segment, thence regularly 

 tapering to the pygidium. 



Pleura relatively broad, Hat for about one-half their width and thence 

 rounded to the lateral margins. 



Each segment lias a slight forward curve along the axial line, being sulcate 

 on the pleura' and having the anterior limb abbreviated by the beveled 

 planes of articulation. 



Pygidium sub-triangular, depressed-convex or flattened. Posterior extremity 

 produced into a stout, upwardly curved spine, usually short, but sometimes 

 equaling the pygidium in length. Length, including the caudal spine, equal 

 to the width. 



Axis having less than one-third the width of the shield on the anterior 

 extremity, regularly tapering to an obtuse, broadly rounded termination, and 

 composed of from nine to fourteen broad, Hat, transverse annulations. 



Pleura broad and rounding more or less abruptly to the margins, bearing 

 ,| - llt '"' lllm ' wide, flattened annulations, which become obsolete just within 

 the border. Wherever the crust is retained the annulations are seen to be 



