74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



but is typical of the genus. The glabella tapers to a rounded front. 

 A keel is clearly defined and faint shadows indicate glabellar furrows. 

 Brim, one-third the length of the glabella, has a more clearly defined 

 rim than usual. The fixigenes are narrow and the palpebral lobes 

 rather large. 



In the pygidium the axis, with fairly deep furrows, occupies about 

 half the pygidial length. The pleural lobes slope down rather gently 

 to the wide border which assumes a horizontal position. 



Sullivan formation; (loc. 651 ) Glacier Lake Canyon Valley, 48 

 miles northwest of Lake Louise, Alberta. 



Holotypc.—U.^.NM. No. 108768a; paratype, No. 108768b. 



COOSIA DAKOTENSIS, new species 

 Plate 13, Figures 29-31 



Although this large species is abundantly represented, only a few 

 unbroken examples of each part have been freed from the matrix. It 

 occurs in thin limestone lenses composed chiefly of trilobite fragments. 

 Some of the fragments show the heavy doublure characteristic of 

 the genus. 



The cranidium is fully typical of Coosia in its tapering unfurrowed 

 glabella, wide concave brim, and narrow fixigenes. The brim width 

 is considerably more than half the glabellar length. It is without an 

 anterior furrow, but the heavy doublure causes a thickening in the 

 anterior portion. Fixigenes and eyes are normal in development. 



Libragene large, with an elongate ocular platform and a heavy rim 

 that extends into a long, heavy, nearly straight genal spine. Brim on 

 both the cranidium and libragene striated. 



Pygidium normal, with the axis occupying about half the pygidial 

 length. Axial rings well defined, and on exfoliated specimens the 

 pleural furrows are visible. 



Deadwood formation ; (loc. 17J) Galena, Black Hills, South Dakota. 



Holofype. — U.S.N.M. No. 108769a; paratypes, Nos. 108769b, c. 



COOSIA TRIDENTENSIS, new species 

 Plate 15, Figures 12-17 



This species is abundantly represented in the small collection from 

 this locality. Unfortunately the rock is shattered with injection of 

 calcite veins, which with the crowding of the fossils accounts for the 

 difficulty in getting complete specimens. 



The glabella tapers rather rapidly to a rounded front. Lighted 

 from certain directions it ap]5ears to be sharply truncate because of 

 the contour of the anterior lobe. Another peculiar feature is the 



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