604 Annals ok 'jhe Carnegie Museum. 



It is unfortunate that the glabella of Cybele icinchelli is not known, 

 as that was described from a much larger specimen, and is i^robably from 

 a higher horizon than any of the other specimens of this genus found in 

 this country. The ])ygidium of that species differs from the pygidium of 

 Cyhele el/a in lacking the large first rib on the ])leura, and in having 

 only a very few furrows on the sides of the axial lobe. Neither does 

 our specimen show any signs of the long spines on the ends of the sixth 

 thoracic segment, but that may be due to imperfections in the material. 

 Both species have rather coarse spines at the genal angles. 



From all the Russian species of Cybele, our species differs markedly, 

 not only in the ])resence of a genal sjjine, but also in the structure of 

 the glabella. With the exception of Cybele Grezvingki Schmidt, 

 Cybele Kutorgce Schmidt, and Cybele RcvaUeiisis Schmidt, all the 

 Russian species have the glal^ellar furrows sharply impressed. In the 

 three species just mentioned, the glabellar furrows are represented by 

 pits which are nearly isolated, but the pit.s are not connected as in 

 Cybele [>rii)ia or Cybele el la. 



Aside from the structure of the glabella, the American and Russian 

 forms are very similar, and, as Ruedemann has remarked, it is i)rob- 

 able that the American forms have been developed from European 

 types. 



