36 



by a shorter quadrangular plate, which is succeeded by a short, 

 axillary plate. The second bifurcation of the rays takes place 

 on the fourth plate, from the first axillary plate, in all the rays 

 except two, and in these it takes place on the fifth plate. Our 

 specimen is not preserved so as to show any further divisions 

 of the arms, if any take place. 



The first azygous plate is long and narrow like a subradial, 

 and extends down deep into the columnar cavity, between a 

 subradial and the under sloping side of the first radial on the 

 right and rises a little aboye the subradial. The second plate 

 truncates the subradial, separates the first radials and extends 

 to the top of the first secondary radial on the right and to the 

 middle of the second secondary radial on the left. It is followed 

 by a much smaller plate, and it, in turn, by a small triangular 

 plate. 



This species is distinguished from Z. magnoliiformis, the type 

 of the genus, which it seems most to resemble, in several par- 

 ticulars, one of which is sufficient to distinguish the species. In 

 Z. magnoliiformis, the arms bifurcate on the third and fourth 

 plates, in this species they bifurcate on the fourth and fifth 

 plates. The azygous side of Z. magnoliiformis has never been 

 illustrated ^and we have no specimen of that species with which 

 to make a comparison, but, judging from the description given, 

 in the Geo. Sur. of Iowa, Page 544, the azygous areas in the 

 two species are not alike. The subradials have not the same 

 form according to the illustration of that species, by Hall. Our 

 species is more robust and the basal cavity seems to be deeper. 

 It has some resemblance to Z. depressus, a diagram of part of 

 which is in the Geo. Sur. of Iowa, Page 546, but the azygous 

 area will at once distinguish it. 



Found in the Kaskaskia Group, at Flag Pond, Virginia, and 

 now in the collection of Win. F. E. Gurley. 



ZEACRiNUS NITIDUS n. Sp. 



Plate VI, Fig. 3, azygous view; Fig. 4, view of the same 

 specimen, opposite the azygous side. 2 he speci- 

 men is somewhat flattened. 



Species below the average size, much constricted above the 

 ealyx, arms proportionally large and coming to a point at the 



