POTSDAM PERIOD. 



189 



been found united to the head; b, the pygidium. Other species of this Pri- 

 mordial genus occur in northern Vermont, Labrador (Straits of Belle Isle), 

 and Texas. Fig. 242, Biccllocejihalus Minnesotensis D. D. Owen, a trilobite six 

 inches long, from Lake St. Croix, Minnesota; fig. 243, D. Iowensis, pygidium, 

 natural size, from near the mouth of Black River, Iowa. The name of this 



Fig. 245. 



Fig. 245 A. 



Track of a Trilobite (X Yd- 

 Fig. 245 B. 



Paradoxides Harlani (X %)• Protichnites 7-notatus (X/^)« 



genus is from SikeWti, a shovel, and K£([>a\r], head. Fig. 245, Paradoxides Harlani, 

 reduced, from Braintree, near Boston. P. Vermontana and P. Thompsoni are 

 species from Georgia, Vt., and the Straits of Belle Isle ; the latter is over four 

 inches long. P. Bennetii is a large species from Newfoundland. Bathi/urus 

 parvulus and B. senectus B. are from the Straits of Belle Isle. Pcltura hqlopyga 

 is another trilobite, three and a quarter inches long, from Georgia, Vt. Species 

 of Agnostus, Arionellus, and Dicellocc2)halus, besides Cqnocephalus, occur in 

 Texas. Arionellus? Oweni M. & 11. is from the Black Hills, Dakota, and the 

 Big Horn Mountains. Paradoxides asajrfwides Emmons, is a large species 

 from the Taconic slates of Washington co., N.Y. ; and Microdiscua quadricostatns 

 Emmons, a small trilobite, from Augusta co., Va., remarkable for a very narrow 

 glabella as long as the head, and a short body. Fig. 245 A, section (referred to 

 on p. 185) of a track, probably of a large trilobite, from near Perth, Canada, 

 described by Logan, who names it Clitnaetichnites Wilsoni. Fig. 245 B, track, 

 supposed to be Crustacean (p. 185), called Protichnites 7-notatus. 



