NO. 9 NEW CAMBRIAN TRILOBITE FAUNULE — RASETTI 27 



with the axial furrow. Glabellar and occipital furrows entirely obso- 

 lete. Cheeks convex ; border wide, convex, downrolled into the dou- 

 blure. Posterior cephalic border with a blunt tooth, extended at the 

 genal angle into strong spine. 



Pygidium similar in shape to cephalon, more tapered posteriorly. 

 Axis reaching posterior border, un furrowed, well defined by axial 

 furrow. Border furrow well impressed ; border flat, fairly wide ; dou- 

 blure sloping inward at about 45° to vertical, with serrated margin. 

 Size large for an Eodiscid. 



Type species. — Litometopus lotigispinus Rasetti, new species. 



Occurrence. — Late Lower Cambrian of New York. 



Discussion. — This form is a close relative of Serrodiscus, sharing 

 with that genus the shape of the glabella, the general structure of the 

 pygidium, and a slightly serrated doublure. Chief dijfferences are 

 the width and convexity of the cephalic border, the entire lack of 

 preglabellar field, the unusual tooth at the posterior cephalic border, 

 and the strong genal spine. The last two features also distinguish 

 the genus from Cobboldites comleyensis, which has an equally long 

 glabella and a similar pygidium. The very large size of Litometopus 

 contrasts with the small size of the known examples of Cobboldites. 



LITOMETOPUS LONGISPINUS Rasetti, new species 

 Plate 3, figure 3 ; plate 8, figures 1-9 



Available material. — A few cephala and a larger number of pygidia. 



Description. — Cephalon 1.3 times wider than long, with uniformly 

 rounded anterior and lateral outline. Glabella widest at the undif- 

 ferentiated occipital ring, with slightly concave lateral outline, 

 rounded in front, well defined by the axial furrow, convex in both 

 directions. Cheeks very convex, sloping down steeply to the deep 

 border furrow. Border wide anteriorly, narrowing toward the genal 

 angle, convex, downrolled into doublure, showing a pair of small 

 lateral spines somewhat anterior to the cephalic midlength. Border 

 furrow becoming very shallow at the genal angle ; genal spine strong, 

 curving inward, not greatly tapered, when complete probably equal- 

 ing the cephalon in length. Posterior border furrow well impressed ; 

 posterior border straight from axial furrow to near base of genal 

 spine, where it forms an obtuse tooth set off by a narrow, short 

 furrow. Surface of test sparsely punctate, more distinctly in larger 

 individuals. The largest (holotype) complete cephalon has a length 

 of 8.3 mm and a width of 10.7 mm. However, a large cephalon in 

 the collection, crushed by the slumping of the sediment in such 



