OF DENISON UNIVERSITY. 
97 
The first is the well known Calymene Blu?nenbachii of the Wen- 
lock Series of England. The forms of this species represented by 
Salter (Paleont. Soc. Vol. 1863, pi. 8, figs. 7-16; pi. 9, figs. 1-5, var, 
Auctorum), approach the American species. The head represented on 
plate 9, fig. I, from the Lower Wenlock Grits (Niagara Series), shows 
a wide frontal margin similar to the Ohio and Georgia forms ; the head 
figured on plate 9, fig. la, has a straight anterior margin with a nar- 
row limb, whereas the American forms have this part rounded with a 
comparatively broad limb. The pygidia figured by Salter, plate 8, fig. 
8c, and plate 9, fig. ib, have a general similarity, although the Ohio 
forms show a tendency to extend their side ribs more to the rear, giv- 
ing the pygidium a semi-circular outline. 
The Bohemian Upper Silurian form described by Barrande (Syst. 
Sil. Boheme, Vol. I, pi. 19, figs. 1-19, Calymene diademata, Etage E ) 
represents a form with a broad frontal margin (pi. 19, fig. 12), thick- 
ened and incurved ; whereas, the Ohio species has its frontal margin 
extended, the anterior border of the head forming a broad and even 
curve about the head, turned slightly upwards and not arched in the 
middle, the limb being exceedingly broad and separated from the an- 
terior margin of the glabella by a deep groove. Barrande’s figure, pi. 
19, fig. 18, represents a broadly rounded pygidium, the axis being an- 
teriorly broad, and tapering ’posteriorly, marked by six axial rings. 
The sides are marked by five bifid segments. The Ohio species has a 
semi-circular pygidium, the posterior margin being almost straight. The 
axis is broad anteriorly and tapers posteriorly to a rounded extremity, 
marked by nine well defined axial rings. The sides have five bifid 
segments, and a posterior undivided pair. The anterior segments be- 
ing extended backwards to such a degree as to form a semicircle. 
Angelin’s figures of Calymene spectabilis (Pal. Scand. pi. 19, fig. 5, 
Reg. E), which Salter refers to Calymene Bliimenbachii^ lacks the 
broad frontal margin of the Ohio forms. The pygidium of this species 
as represented by Angelin’s figure shows the common rounded poste- 
rior margin of the English species, Caly 7 nene Blumenbachii. 
The American Calymene Clintoni is distinguished by the smooth 
side lobes of the pygidia. It is found in the Niagara Group shales, at 
Rochester, N. Y., below the falls. 
Calymene 7 na 7 nmillata^ Hall, (Geol. Rep. Wis. 1861, p. 50), from 
the shales above the Trenton Group, has its anterior border extend- 
ed in front of the glabella in a broadly rounded, thickened projection 
