736 



Report ok the State Geologist. 



somewhat broader than the rest and, in the larger specimen, showing a 

 tendency to division along its distal portion. The margin of the pygidium is 

 "without evidence of spines. In general contour this plate is broadly depressed 

 within the slightly elevated periphery, convex over the central region and 

 again sharply depressed about the axis. 



Ornamentation, The entire test is pretty uniformly pustulose, the 

 pustules varying somewhat in size and being coarsest on the glabella and the 

 ribs <»f the pygidium. About the enfolded margins of the cephalon and 

 pygidium the surface is marked by the usual incised inosculating lines. 



Observations. This species is noteworthy not alone for the rarity of all 

 trilobites at this horizon. It is, in all probability, the latest representative 

 of the genus, making its appearance in this later division of Devonian time, 

 subsequent to the first intrusion of Spi/Hfer di&jv/notus and long after the 

 only observ ed occurrence in this country of Olymeni(i. It appertains to a 

 fauna which, considered in its local relations and in correlation with faunas of 

 other countries, characterizes the final stages of the Devonian, and in these 

 we have no other record of the occurrence of Bronteus. In this late survivor 

 of the genus, therefore, we may expect to find structural traits indicative of, 

 or in harmony with its late appearance. We observe that between the earlier 

 ( upper Silurian and early Devonian ) and the later Devonian representatives of 

 this genus there are contrasts in the form of the glabella, the outline of the 

 pygidium and the nature of its ribs. Thus, the glabella (<>r we should rather 

 say the cranidium, as the distinction depends on the varying distance between 

 the facial sutures) is very wide anteriorly, the dorsal furrows being highly 

 concave within the ocular nodes (compare JS. palifer, Beyr., Lower Devonian, 

 Zittel's figure, Grundziige der Palreontologie, p. 473, fig. 1,279a; Katzers 

 figure, Geologie von Bdhmen, p. 1,023, fig. 45)8-4; B. <ampanif<i\ Beyr,, 

 lower Devonian, Bey rich's figure, Einige bohmische Trilobiten, Plate, fig. 6 ; 

 B. Partschi, Barr., upper Silurian, Katzers copy of Barrande's figure, op. cit., 

 p. 937, fig. 377-2 ; B. viator, Barr., low er Devonian, Novak's figure in 

 Katzer, op. cit, p. 1,036, fig. 548-1 ; B. <i<-<tm<is. Hall, Niagara group, Twentieth 

 Annual Report New York State Cab. of Natural History, PI. H, fig. 19; 

 B. lunatus. Billings, Trenton limestone, Geology of Canada, p. 188, fig. 187, 

 and Clarke's figure, Geological Survey of Minnesota, Vol. Ill, Part 2, p. 725, 

 fig. 43). In all of these and numerous other recorded examples the feature 

 referred to is strongly manifested. If on the other hand, we turn to species 

 of the middle Devonian, the narrowing of the glabella and the interval 

 between the facial sutures becomes evident (see />. jhtln-Uifer, Goldfuss, 



