NIAGAKA GROTJP. 315 



Fig. 2 a. The posterior part of the buckler, showing the lateral lobes and the prominent central 



one. 

 Fig. 2 6. The front of the same, a view directly opposite to the previous one. 

 Fig. 2 c. Profile view of the same. This figure is incorrectly represented by the engraver, who 



has confounded the posterior lobe or protuberance with the expanded portion below 



the eye. The pustulo-spinous protuberances are likewise not properly represented in 



the engraving. 



Position and locality. The specimen figured was found in the shale of the Niagara group 

 near Albion, Orleans county. 



Genus PROETUS (Steikinger, Loven). 

 JEONIA, BuRMEisTKR ; FORBESIA, M'Coy. 



The description given by Burmeister of the Genus Proetus, would not admit the two fol- 

 lowing species, on account of the spiniform projections of the posterior angles of the cephalic 

 shield. In other respects, however, particularly the undivided glabella, facial suture, etc., the 

 description correponds with our specimens. 



The Asaphus stokesii of Murchison, with which one of ours is allied, if not identical, has 

 been referred by Loven to the Genus Proetus ; while Burmeister has placed it under his 

 Genus ^Eonia, an important character of which is a lobed glabella, and the angles of the 

 buckler projecting in long spines. 



It is quite evident that there is some confusion here, which can not be satisfactorily cleared 

 up at present. I have no doubt but there are two distinct genera here confounded, and that 

 jEonia (taking the characters of the glabella as a guide) will be found in our Hamilton group, 

 and is probably a devonian type ; while the one with smooth, unlobed glabella and buckler, 

 and spinous posterior angles, will characterize our middle silurian strata. 



675. 1. PROETUS CORYCCEUS. 



PL. LXVII. Fig. 15. 

 Asaphus coryc(EUs. Conrad, Jour. Acad. Nat. Science, Vol. viii, pag. 277, pi. 16, fig. 15. 

 Sub-oval ; width about two-thirds the length ; head a little more than half the length of the 

 body ; axis wide and rather prominent, tapering abruptly in the caudal shield ; cephalic shield 

 crescentiform, with long posterior spines reaching to the sixth articulation of the thorax ; border 

 of shield striated parallel to the margin ; glabella prominent, broad in f-ont and narrower be- 

 hind ; cheeks convex ; eyes large, reniform, placed near the glabella, and reaching to the 

 neck-furrow below ; facial suture turning from below the base of the eye abruptly outwards, 

 and coming to the base of the shield half way between the axal furrow and the margin ; axis 

 of the thorax prominent, convex, and wider than the lateral lobes, except in the last articu- 

 lations, where it is equal in width to the lateral lobe ; articulations of the lateral lobes grooved 



