722 THE PALEONTOLOGY OF MINNESOTA. 



I Hiliii;is1ii-i (ii'ljiciuidatus. 



BUMASTUS ORBICAUDA.TUS Billings (sp.), 1859. 



Illtenus orbicaii'l'itu* liir.i.i.vas, 1859. Canad. Nat., vol. iv, p. 379. 



Illcenus orbicaudatus BILLINUS, ism;. Out. Silur. Foss. Antirosti, p. 27, flg. 10. 



There is a single cranidium from the Galena shales at Wykoflf, Minnesota (Dr. 

 Robbing' collection), which appears to represent this species, described originally 

 from the Trenton or Hudson 1 fiver horizon at English Head and elsewhere, Anticosti. 



Fi^. 3G. Binmtiitiis orlrii-iiiulatus Hillings. Galena shales. Kcnynn. 



HUMUS/UN orbicaudatus and B. frentonensis resemble each other in many respects, 

 though specimens of the latter are of decidedly smaller size and greater convexity of 

 cephalon. The Wykoff specimen measures 20 mm. in length, and 26 mm. in width 

 across the base. Certain large, smooth, unsegmented pygidia from the Galena 

 shales at Kenyon are probably parts of the same species. 



Genus BATHYURUS, Billings, ISO!). 

 BATHYURUS KXTANS Hall, (sp.), 1847. 



Asaphus? extans HALL, 1847. Paleontology of New York, vol. i, p. 228, pi. 60, Iljjs. '2<t < . 

 Asaphus extans HALL, 1850. Third Ann. Report N. Y. State Cab. Nat. Hist, p. 174, pi. :t, li^s. \ ,-. 

 Bathyurus extans BILLINGS, 186.'). (ieol. Canada, p. If.:!, Iltf. 114. 

 cf. B. longispinus WALCOTT, 1876. Twenty-eighth Rept. N. Y. State Mus., p. 94. 



This species was founded on a pygidium from the Birdseye limestone, professor 

 Hall's description of 1847 being supplemented by an account of the cephalon and a 

 portion of the thorax, in 1850. Mr. Billings proposed the genus Bathyurus in 1851) 

 (Canadian Naturalist, vol. iv, p. 364), taking this species as its type and giving, in 

 1863, the first figure of the entire test. Mr. Walcott's B. longispinus, from the Blac.U 

 1 fiver limestone of Ifnssia. X. V., and the Trenton horizon at Platteville, Wisconsin, 

 appears to me the same species. 







R. '''. I'-.rtinn nf head of Bathyurus txtunx Hall, Camion Falls. 



Among the specimens loaned for my study by the late Mr. Scofield, is one of this 

 species retaining most of the cephalon and an impression of part of the thorax and 

 pygidium, from the lower Trenton or Birdseye horizon at Cannon Falls, Minnesota. 

 It, i* the only example observed which may be safely referred to the species. 



