606 THE PALEONTOLOGY OF MINNESOTA. 



[Clidopliorus. 



marked by regular sharp, though fine, concentric striae in the posterior half, the 

 anterior half appearing smooth. Hinge and interior unknown. 



The single specimen of this form seen from Minnesota, agrees so well in its 

 outline and general appearance with Walcott's figures of T. hamburgensis that I am 

 obliged to refer it to his specieis. It should be remarked, however, that the surface 

 of the Nevada types of the species is described as presenting "a smooth, glistening 

 appearance," giving them "the character of some of the Linguloid shells," and that 

 it is marked by not only concentric lines but also by " very fine, often scarcely per- 

 ceptible radiating striae," all of which is wanting on the Minnesota specimen under 

 consideration. But, as these differences may all be due to different methods of 

 preservation, I have not taken them into account. 



Respecting the generic position of the shell there may be some doubt, because 

 we have as yet no knowledge of the interior. Nor does the species seem to fit very 

 well into any of the sections into which the genus has been divided. Certain it is 

 that it is not very closely related to any of the numerous species described. Perhaps 

 it is the most like C. socialis, with which it is also associated, but it will be distin- 

 guished readily enough by its shorter and rounder form, fuller umbones and more 

 distinctly striated surface. 



Formation aiid locality. Upper part of the middle third of the Trenton shales, Chatfleld, Minnesota. 

 The types of this species are from the upper part of the Pogonip group, Eureka District, Nevada. 



Genus CLIDOPHORUS, Hall. 



Clidophorus, HALL, 1847. Pal. N. Y., vol. i, p. 300. 



Compare Nuculites, CONRAD, 1841. Ann. Rep. Geol. N. Y., p. 49; and Cucullella, McCov, isr,:,. 



I prefer not to characterize this genus at the present time, nor to express any 

 definite opinion respecting its relations to Cucullella, McCoy, and Nuculites, Conrad, 

 for the simple reason that I have had no opportunity to study the typical species of 

 the genera. It should be stated, however, that many authorities regard the three 

 names as synonymous and that, unless new distinctive features are brought out, 

 their views cannot be successfully combated. 



CLIDOPHORUS CONSUETUS Ulrich. 



ri.Aii: xx.xvn. IMI.S. .1^ uii 

 Clidophorus consuetus ULRICH, 1892. Nineteenth Ann. Rep. (Icol.and Nat. Hist. Sur. Minn., p. 2i'l. 



Shell above the medium size for the genus, transverse, moderately elongate- 

 ovate, rather strongly convex, the length equaling nearly twice the hight. Beaks 

 small, incurved, flattened. Dorsal line convex, sloping downward behind the beaks 



