they unite behind it, and continue as two short sharp spines. 

 Between the fifth rib and the side of the axis there is a narrow 

 smooth space with a faint groove on the inside, it extends 

 round the apex of the axis and seems to be the rudiments of a 

 sixth pair of ribs. 



The principal differences between these species lies in the 

 character of the lateral lobes, Encrinurus Americanus having 

 three free and three united ribs in the pygidium ; whereas En- 

 crinurus elegantulus the first four are free and the other two 

 unite at their extremities, the side ribs originate at the first axial 

 ring, the second pair at the second, the third pair at the fourth, 

 and the fourth pair at the sixth ; whereas in the new species 

 the third pair originate between the 5 and 6 axial ring, and the 

 fourth pair between the 7 and 8. The minor differences with 

 regard to the nodes on the axis may be due to the state of 

 preservation. 



The pygidia of Zethus verrucosus and ZetJms hcllatula de- 

 scribed and figured by Dr. Volborth (Russ. Mineral. Gesellsch 

 Vehandl., 1848, p. 4, pi. 1, figs. 3, 4 and 7), are in general 

 form similar to those of JS'rimjiMrws Americanus and Encrinuriis 

 elegmitulus. They all have from 4 to 6 side ribs, the anterior 

 ones being free, and the last two or three united at their ex- 

 tremities in rear of the axis. The axis in the Russian species 

 has from 16 to 18 axis rings, the first 4 or 5 anterior ring only 

 bearing side ribs, whereas the American species has from 20 to 

 24 rings, the first 8 to 13 rings extending across it, the side 

 lobes extending down in one species at least to the 8 arial ring. 



The Russian species have a notched axis, Avith nodes along 

 the smooth central part. 



Geological Position. — -Clinton Group, Taylor's Ridge, west of 

 Catoosa Station, Catoosa Co., Georgia. 



Calymcne rostrata, Vogdes. 



CaUjinene rostrata, Vogdes, 1879, Am. Jour. Sc, Art. III., vol. xviii, ji. 477. 

 Calymene rostrata, Vogdes, 1880, Acad. Nut. Sc, Pliila., Proc, p. 176, tigs. 1-2. 



This species differs in one aspect from the usual forms classed 

 under the gQun^ Calymene, in having a projecting process aris- 



