42 NEW YORK STATE MUSEUM 



Dorsal furrows distinct, broad and deep, narrowing forward and 

 extending to the frontal border. Fixed cheeks slightly promi- 

 nent, trapezoidal in outline, nearly flat in the middle part and 

 bending rather abruptly into the dorsal furrow and to the 

 marginal border; each cheek provided with an " eye line," which, 

 arising in the dorsal furrow below the first glabellar pit, extendi® 

 in the direction of the genal angle, culminating near the middle 

 of the cheek in an eye tubercle and becoming then indistinct. 

 Occipital furrow broad and shallow, widening on either side of 

 the glabella. Occipital ring a uniformly narrow ridge which in 

 the axial lobe rises to a semicircular plate (base of spine?). 



Surface of glabella coarsely pitted; cheeks pitted along the 

 border and strongly reticulate in the middle. The meshes of the 

 reticulation are largest on the cheeks; dorsal furrows and occipi- 

 tal ring smooth. Marginal border in front of the glabella inclined 

 to base at an angle varying between 80° and 90°, but becoming 

 less inclined posteriorly; in front of the cheeks for about half of 

 its width moderately convex, then equally concave with the mar- 

 gin upturned. The convex portion of the border in front of the 

 glabella is occupied by four concentric rows of circular funnel- 

 shaped perforations, which posteriorly increase by interplanta- 

 tion to seven or more rows; the concave portion bears a row of 

 radiating elongated perforations 1 ; the rows of perforations are 

 separated by filiform, strongly projecting concentric ridges, 

 which toward the genal angles become less distinct. 



Free cheeks not observed. 



Thorax not well preserved, apparently consisting of six seg- 

 ments, axis broad, moderately convex, decreasing in width more 

 than one third; axial grooves shallow; pleurae not observed. 



Pygidium roundish subtriangular, with an axis in a small speci- 

 men that is broad at the beginning, slightly tapering and ending 

 bluntly; more acutely tapering in larger specimens; the small 



i Dr D.-P. Oehlert has demonstrated in his valuable paper entitled: Sur les Trinucleus de l'Ouest 

 de la France (Soc. geol. de France. Bui. 3e serie. 1895. 23, p. 299) that the apparent perfora- 

 tions of the limb of Trinucleus are only the result of an unfavorable preservation; and that, in fact, 

 the limb or doublure of Trinucleus is imperforate, but possesses cavities, produced by the invagina- 

 tion of the tegument of the limb. As the tegument mostly fails of perfect preservation, these 

 double-conical cavities appear opened at their dorsal and ventral apexes. 



