CRUSTACI. A. 7 



Binnewater, Ulster county." This reference is probably correct, as the matrix 

 of the larger trilobite shows a well-defined specimen of Spirifera arena . an 

 Oriskany species, and Mr. Whitfield has mentioned the occurrence of a young 

 individual of Strophodonta magnified upon the smaller specimen. 



HOM IL0N0TUS DeKAYI. 



PLATE II, FIGS 111 i PLATE III, FIGS l 5; l'l.vii; l\, FIGS. l-fi; ISO PLATE V, PIGS. 1-10. 



Dipleura h iayi, Green. Monog. T b N irth '. ■■ ca, p. 79. IS32. 



Nuttainia sparsa, Eaton. Geological I , p. 34. is 



Dipleura Dekayi, Vandxem. Geologj of New Fork. Survey G .' I I, fig, 1. IS42. 



Dipleura Dekayi, Hall. Geologj of New York. Survey Fourth Geol. Hist., p. 205, fig. I. 



Bmnalonntus Dekayi, Emmojjs. Manual of Geology, pp. 146, > IT. fig . 134, 135. I860. 



Hbmalonotus Dekayi, Hall. Fifteenth Rept. N. Y. State Cab Mai H t., p. 113. 1862. 



Homalonotus Dekayi, Hall. Illustrations of Devonian F ii, iii, iv, v. 1 st»;. 



General Form and Proportions. Elongate, linguiform, anterior and posterior 

 extremities produced and sub-angulate ; lateral margins nearly straight and 

 approximating posteriorly. Length to width about as 2 to I. 



Surface depressed-convex or flattened, obscurely trilobate, abruptly de- 

 flected along the lateral margins. 



Cephalon broadly sub-triangular in outline, posterior side the longest : angles 

 rounded. In the usual condition of preservation the lateral margins approach 

 each other at an angle of ninety degrees, making, at the basal margin, an 

 angle of forty-five degrees. With the retention of normal convexity, the 

 shield is nearly equilateral. Length to width as 1 to L.9. The surface is 

 normally depressed-convex or flattened, deflected beneath the ocular nodes; 

 trilobate; frontal and lateral areas narrow, the former produced into a 

 short prora. 



The facial sutures take their origin on the lateral margins of the doublure in 

 front of the genal angles and pass inward, parallel to the posterior margin 

 of the cephalon, to the eye, thence forward with a broad curve inward to 

 the anterior margin at the base of the prora, bending tin <■ ce on to the epis- 

 tomal doublure, meeting at its inferior margin. The branches of the facial 

 suture are united on the upper surface of the prora by a straight transverse 



