409 



of the hypostoma not forked, and the glabella well defined by the dorsal 

 furrows. It somewhat resembles both Megalaspis and Niole (Angelin), 

 in the form of the glabella, but the hypostoma is precisely like that of 

 Qgygia. I have some evidence to show that the head is composed of 

 three pieces only, as in Dikelocephalus. The species heretofore described 

 are, B. amplimarc/inatus, B. conious, and B. Cyhele, from the Calcifer- 

 ous Sandrock : — B. Angelini, Chazy ; B. extans, (^Asaphus extans. Hall,) 

 as yet known only in the Black river limestone, and B. spiniger, {Acid- 

 aspis spiniger, Hall.) This latter species occurs both in the Black River 

 and Trenton, in Canada. 



The following species are referred to this genus provisionally. I am not 

 at all satisfied that they belong to the genus, but I know of no other to 

 which they bear so near a resemblance. 



Bathyurus capax. (JSf. sp.) 



Fig. 389. 



Description. — Head convex, forming a depressed quarter of a sphere. 

 Glabella oblong, separated from the flat, sloping rim of the front margin 

 by a narrow angular groove ; sides gently concave, nearly straight, with 

 a short obscure outward curve opposite the eye, slightly converging tow- 

 ards each other from behind, forwards. The neck furrow is represented 

 by an obscure transverse impression, which occupies the middle third of 

 the width of the glabella, but does not reach all across. The anterior and 



Fig. 390. 



Fig, 389. Fig, 391. 



Fig. 389. — Bathyurus capax. Tlie lower figure is a longitudinal section, showing 

 the convexity of the glabella and the flat sloping rim of the front margin at a. 



Fig. 390. — Bathyurus dubius. 



Fig. 391. — Bathyurus bituberculatus. 



BB 



