63 



NUCLEOGUINUS VENUSTUS, U. Sp. 



Plate VI, Fig. 20, azygous side view; Fig. 27, summit view of 



same specimen from Louisville; Fis^. 2'S, side view; Fig. 20, 



basal view of same; Fig. SO, side view of another 



specimen, all from Columbus, Ohio. 



Body elongate, subelliptical, flattened or slightly concave in 

 the interradial spaces, obtusely rounded at the pseudambulacra; 

 greatest width about the middle. 



Base nearly fiat. Basal plates slightly convex. Radials 

 rather long and embracing the lower end of the pseudambu- 

 lacral fields, and the node, which terminates the pseudambulacra, 

 in the central part of each plate. Pseudambulacral fields nar- 

 row, uniform, in width, and separated by a sharply angular 

 depression. Interradials extend to the summit and are centrally 

 depressed in lanceolate outline, but no suture has been discov- 

 ered, by the side of this lanceolate ornamentation, to show that 

 it is a plate, as described by Lyon, in the Geological Survey of 

 Kentucky. Possibly the sutures are anchj'losed. This lance- 

 olate depression has a fine, longitudinal furrow, in the center. 

 On each side of the lanceolate depression the surface is beauti- 

 fully ornamented with longitudinal, crenulated lines. 



Azygous interradius a little wider than the regular areas, and 

 the azygous plate stands out prominently beyond the pseu- 

 dambulacra toward the summit. The longitudinal, lanceolate 

 depression on the azygous plate, that would seem to corre- 

 spond with the lanceolate depression, in the regular areas, does 

 not correspond with the outline of the azygous plate. On the 

 contrary, the azygous plate is considerably larger and occupies 

 fully two-thirds of the whole azygous interradius. The sides 

 are beveled downward from the azygous opening to the suture 

 line and the summit is notched for the orifice. The interradial 

 plate in the azygous area is narrow on each side, pointed in the 

 lower part, notched for the azygous orifice and reaches the 

 summit. The surface is ornamented as in the regular areas. 



There are two elongated apertures, at the summit of each 

 pseudambulacra, which are indicated by a raised rim in the ad- 

 joining interradials. The central part of the summit is covered 

 by numerous plates. 



