38o 



NORTH AMERICAN INDEX FOSSILS. 



IX. Eleutherocaris Clarke. 

 Carapace elongate, snbquadrate, truncated anteriorly, incurved 

 posteriorly; with broad, obscure nodes in the cephalic region; very 

 short, single lateral carinse in anterior portion ; telson slender, cer- 

 copods of equal length ; surface more or less strongly tuberculated. 

 Devonic. 



19. E. whitfieldi Clarke. Devonic. 



Cephalic region with broad, low nodes, lateral carina very short, 

 oblique and situated anteriorly, both ends truncated. (Type of 

 genus.) 



Upper Devonic (Naples shales) of New York. 



X. Elymocaris Beecher. 

 Carapace of two valves with evenly convex and smooth surface, 

 without carina, but w^ith long hinge line, convex posterior margin, 



Fig, 1684. Elytnocaris siliqua, the FiG. 1685. Tropidocaris bicarinala, 



carapace with valves open, showing nie- the carapace expanded, showing median 



dian lanceolate plate and rostrum, X |- lanceolate plate and rostrum, X f- {^^' 



(After Beecher. ) ter Beecher. ) 



and obscure cephalic nodes; median lanceolate plate and rostrum 

 present; two abdominal segments are exposed, with short caudal 

 plate continued in a broad convex and rapidly tapering telson ; 

 cercopods bearing setae on their inner margin. Devonic. 



20. E. siliqua Beecher. (Fig. 1684.) Devonic. 



Rostrum projects slightly beyond the valves and extends back- 

 ward to optic node ; widest at about posterior third of its length, 

 and bearing two longitudinal carinse; median plate widest just in 



