TRENTON CONGLOMERATE OF RYSEDORFH HILL 63 



being twice as large as the other, but they are otherwise too 

 closely alike to allow a specific separation. The glabella and rim 

 are apparently completely smooth, but show under the glass fine 

 transverse striae. Neck ring nearly flat, depressed, with a cen- 

 tral tubercle; occipital furrow distinct, nearly straight. Sutures 

 begin at the anterolateral angles of the margin, extend in the 

 direction of the second glabellar lobe to near the glabella, and 

 then curve backward. Only a few species of this genus are 

 known from the Lower Siluric of America, viz: 



C. g i r a r d e a u e n s i s Shumard, 1 which, though approaching 

 this species in the outline of the glabella, differs distinctly by the 

 much narrower frontal limb of the fixed cheeks, which in C. 

 matutina is almost as wide as the glabella, while in 

 C. girardeauensis the interspace between the glabella 

 and the rim is not broader than the latter. 



. ? brevimarginata Walcott, from the Pogonip of the 

 Eureka district of Nevada, has an entirely different glabella, 

 which is conic in shape, and the frontal limb consists only of a 

 narrow rim in front of the glabella, and 



C? galenensis Clarke, from the Galena shales at Cannon 

 Falls Minn., which, though possessing a similarly formed gla- 

 bella, lacks the basal glabellar lobes. 



The lower Siluric of Europe is also very poor in species of 

 Cyphaspis. According to Freeh a representative not yet spe- 

 cifically determined is reported from the Chasmops limestone 

 of Sweden. Barrande describes a similar species as C. sola, 

 from the etage D, at Koenigshof, which comes nearest to the 

 species from Rysedorph hill, specially in the width of the frontal 

 limb and the direction of the anterior part of the suture line, but 

 the glabella is not so nearly square in front, and the basal lobes 

 are a little more separated from the glabella. It approaches in 

 this feature more the C. girardeauensis. Pompecki 

 describes and figures a similar form as Cyphaspis 

 p a r v u 1 a 2 from glacial boulders of the province of East 

 Prussia, probably derived from the Phaseolus kalk. (Group 5) 



i Geol. Mo. 1855. p. 197, pi. 8, fig. 11. 



2 Triloblten-fauna der Ost- und Westpreussischen Diluvialgeschiebe, pi. 6, fig. 28. 



