CRUSTACEA— PHYLLOPOD A. 



331 



2. E. dawsoni Jones. Mississippic. 



Elongate, length about one and two thirds times height ; beak in 



anterior third, in front of which shell slopes abruptly; posterior 



Fig. 1648. 



Estheria niembranacea, exterior and interior views, X 4> except middle 

 which is X 8. (After Clarke. ) 



end subtruncate, slightly produced below the hinge line. 



Horton beds of Nova Scotia; also Scotland. 

 3. E. ortoni Clarke. (Fig. 1649.) Carbonic. 



Beak more anterior than preceding; anterior end rounded; con- 

 centric striae distant, few ; irregular radiating and branching ridges 

 on lower part of shell, and strong node in umbonal region. 



Fig. 1649. 



Estheria ortoni, two left and a smaller right valve, X ^• 

 (After Clarke.) 



Lower barren beds (Conemaugh) of Ohio (with Leaia tricar- 

 mata) . 

 4. E. ovata (Lea). Triassic. 



Similar to E. ortoni (Fig. 1649, ^) but about twice as large, 

 and the beak nearer the anterior end which is regularly rounded; 

 there are no radiating ridges and the valves are equal. Surface 

 finely pitted, and with strong concentric lines. 



Newark formation of North and South Carolina, eastern Vir- 

 ginia and Pennsylvania. Triassic of Kanab Valley, Utah. 



IL ScHizoDiscus Clarke. 



Carapace bivalve, shield-shaped, with a straight hinge which 

 is in the major axis of the shield; each valve nearly a semicircle; 

 surface marked with concentric ridges. Devonic. 



