756 THE PALEONTOLOGY OF MINNESOTA. 



[ llarpinn inlnnesotensis. 



Surface deeply pitted over the free cheeks and marginal expansions. The 

 punctae are circular, large, attaining their greatest size where the surface is most 

 deeply concave. They appear not to be confluent at any place, but become obsolete 

 on the marginal rim. 



The single specimen observed has an axial length of 12 J mm.; length to end of 

 cheek spine, 23 mm.; basal width 26 mm. 



It is hardly necessary to indicate the particulars in which this fossil differs from 

 the described species of Harpes. The character of the ornamentation, the form of 

 the glabella and its lobation, the absence of broad, lobate expansions about the basal 

 angles of the glabella, the oblique direction of the ocular ridges, as well as the curve 

 of the marginal outline, are all distinctive characters. 



Harpes is a genus which is not abundantly represented in species in any country, 

 though its species are found from the Lower Silurian to the middle Devonian. It is 

 a curious fact that all American species are from the Lower Silurian with the possi- 

 ble exception of the H. consuetus Billings, from the Island of Anticosti, which may 

 belong to a middle Silurian, or a Hudson River-Clinton fauna. In Bohemia none 

 of the forms described by Barrande are from the Lower Silurian but are distributed 

 throughout the Upper Silurian and lower Devonian, while in Germany it ranges 

 through the Devonian faunas disappearing with the fauna of Gonitatites intumescens 

 (Intumescens-kalk). 



The late Dr. Ottomar Novak called attention* to the intermittent occurrence of 

 Harpes in the faunas of the Bohemian basin. Two of the eleven known species 

 appear early in the Lower Silurian (etage DI), but from that horizon to the etage Ea 



Fig. 77. Hypostoma of Harpes venulosus Fig. 78. Hypostomaof J/tirptnaprifcia, enlarged 



Corda, enlarged. 'Etage F,). After Novak. (Etage D,). After Novak. 



including five of Barrande's stratigraphical divisions, there is no evidence of its 

 existence. Novak, suspecting a structural difference between the Lower and Upper 

 Silurian species, which is not apparent from the extei'ior except in a less number of 



Sluillrn :m llypostoinun der bOhra. Trlloblten, No. II. p. 4, pi. I, 1884. 



