CRUST AC EA 



OV nil-: 



UPPER HELDERBERG, HAMILTON. PORTAGE AND CHEMUNG GROUPS. 



DESCRIP I [( >NS < »F SPECIES. 



TIE^ILOIBIT^ 

 CALYMENID^E. 



CALYMENE, Brongniart. 1822. 

 Calymene platys. 



PLATE I, FIGS. 1-9; am. PLATE XXV, Hi, 1 



' lymene platys, Green. Monogr. Trilob. of North America, p. 32. 1832. 

 Calymene platys, Hall. Descrip. New Species of Fossils, etc., p. 54. [861. 



Calymene platys, IIall. Fifteenth Kept. N. Y. state Cab. Nat. Hist., p. S2. 1862. 

 Calymene platys, Hall. Illustrations of Devonian Fossils, pi. i, figs. I -9. 1876. 



General Form and Proportions. Body elongate-sub-ovate, widest anteriorly 

 and tapering rapidly to the posterior extremity. 



Surface convex, laterally deflected, sub-equally trilobate. Length to 

 width as 1.7 to 1. 



Cephalon short and broad, outline crescentic ; length to width as 1 to "J. 5. 

 Margin on the anterior extremity thickened, slightly produced, reflected 

 and broadly infolded to the doublure. Epistomal surface narrow. Genal 

 angles rounded, not produced. Frontal area narrow and obscured by the 

 overarching glabella. 



Facial sutures having their origin on the Literal margins just in front of the 

 genal angles, passing inward with a slight curve nearly parallel to the posterior 



