2/0 



NORTH AMERICAN INDEX FOSSILS. 



lateral lobes. Pygidium small, its axis often reduced to two annu- 

 lations ; the pleural portion produced behind into a splnose flat 

 expansion. Ordovicic. 



35. R. canadensis Billings. (Fig. 1564.) Ordovicic. 

 Genal spines short. Pygidium with four flat spines posteriorly 



and two nodes anteriorly. 



Chazy of New York, Quebec, etc. 



36. R. lingualis Ruedemann. (Fig. 1565.) Ordovicic. 



Fig. 1565. .Remopleurides linjrualis ; 

 top and side view of cranidium and free 

 cheek. (After Ruedemann.) 



Fig. 1566. Neolenus serratus, X Vz- 

 (After Walcott.) 



Palpebral lobes long and narrow, terminating bulb-like poste- 

 riorly. Genal spines long. 

 Lower Trenton of New York. 



XVII. Neolenus Matthew. 



Thorax and usually the pygidium with a spine upon each axial 

 segment and always with each segment terminating in a spine. 



Differs from Parabolina in having longer pygidium, shorter 

 thorax, eye lobes placed farther back and marginal fold wider. 



Differs from Olenoides in the strong tapering of the axial lobe 

 from the anterior portion of the glabella to its posterior portion 

 in the pygidium (in Olenoides the width for the entire distance is 

 nearly unvarying) ; also differs in the more distinct segments of 

 the pygidium, the more triangular outline of the cephalon and the 

 narrow pleural grooves. Middle Cambric. 



