FOSSILS OF THE NIAGARA GROUP. 423 



This species has the pygidia more elongate than B. niagarensis of New 

 York. {Pal. N. Y., Vol. ii,p. 314, PI. Ixx, fig. 3.) The figure given on 

 Plate XXV, fig. 10, is made from a specimen communicated by Prof 

 WiNCHELL under the name of Bronteus occasus. 



Formation and Locality. — In limestone of the Niagara group, at Racine, 

 Wisconsin. 



GENUS ACIDASPIS, Mdrchison. 

 Agidaspis danai. Hall. 



PLATE XXI, FIGS. 8, 9. 



Acidaspis danai, Hall; in Catalogue of Fossils, Geol. Wisconsin, I., p. 423. 1862. 



A. ida, Winch., Mar.; in Mem. Bost. See. N. H., I, p. 106, Plate iii, flg. 13. 1865. 



Head transverse, somewhat quadrangular, about twice as wide as long ; 

 anterior and antero-lateral border ornamented with nodes and short 

 spines. Glabella strongly defined by the dorsal furrows, narrower 

 in front than at the base ; distinctly lobed, the middle lobe larger 

 than the others, separated by deep, strong fmTOws. A strong, 

 slightly diverging spine from each side of the base of the glabella, 

 with a strong node or short spine in the centre. The ocular ridges 

 rise a little in front and one side of the glabella, and continue in 

 a nearly direct line to the base of the eyes which are in a line with 

 the front of the anterior lobes of the glabella. 



This species more nearly resembles Acidaspis vesiculosus, Betrich, as 

 illustrated by Barrande (PI. xxxviii, fig. 13). It differs from that one 

 in being more transverse, in the narrower front of the glabella, and in 

 the straight instead of curving ocular ridges. We have not ascertained 

 whether this species has spines from the posterior borders of the cheeks, 

 which is probable, as in the allied European species. Fig. 9 is from a 

 specimen communicated by Prof Winchell, but I am not able to detect 

 the crenulations on the anterior border, as shown in the figure given by 

 him. 



Formation and Locality. — The original specimen is marked as from 

 Bridgeport, near Chicago, 



