700 THE PALEONTOLOGY OF MINNESOTA. 



LAsaphus. 



Conrad's Calymmene senaria* and Green's C. Uumenbachtf from Trenton Falls, N. 

 Y., are distinct from C. callicephala, as shown by the accompanying figure of the 

 cephalon of the latter, which indicates the decided genal spinules and the long 

 shovel-shaped, not abruptly concave, anterior extension. The Cincinnati form may 



Fig. 3. Outlines of cephalon of Calymmene senaria Conrad, Trenton Falls, N. Y. 



also occur in the Trenton fauna of New York as it does in the Hudson River or 

 Lorraine shales of that region, but the usual Trenton species must retain the name 

 proposed for it by Conrad. 



Among the Minnesota specimens is one to which my attention has been especi- 

 ally directed by Mr. Ulrich, from the Hudson River group near Spring Valley, 

 bearing a cluster of coarse tubercles on each segment of the axis near the dorsal 

 furrows. I am disposed to believe that the original size of these tubercles has been 

 enlarged by a slight deposit of tufaceous matter upon them, but even if this 

 supposition be correct the tubercles must have been larger than usual on this part 

 of the test. The epidermal granulations are seldom well retained in the Ohio 

 specimens but some of the Minnesota examples show them distinctly, while in the 

 New York specimens they are clearly defined over the entire dorsal surface. 



Formation and locality. Galena shales, St. Paul, Cannon Falls; Hudson River group, near Spring 

 Valley, Minnesota. 



Family ASAPHID^E. 



Genus ASAPHUS, Brongniart, 1822. 



Subgenus ISOTELUS, DeKay, 1824. 



The original species of Asaphus, A. expansus Wahlenberg, is of a type which does 

 not appear to be represented in the American faunas. Its lobate glabella, distinctly 

 segmented pygidial axis, and narrow thoracic axis., are sufficiently distinctive to 

 give the term a morphological value when thus restricted. DeKay's term Isotelus, 

 very significant and proposed two years later, includes species with broad axis and 

 obsolete segmentation at maturity. We therefore believe that an excellent purpose 



4th Ann. Kept. Pal. IH-pt.; N. Y. Oeol. Survey, p. 49; 1841. 

 tQp. n/., p. 28, cant 1. 



