502 Observations on the 



Two conspicuous features of this species are its spinose 

 ventral sack, and the great proportional length of the arms 

 to the first bifurcation, which is equal to, or more than 

 half the entire height of the specimen, from the base to 

 the summit of the sack. 



Locality and position, in the upper division of tiie Bur- 

 lington Limestone, Burlington, Iowa. 



Collection of Mr. Charles Wachsmuth. 



Genus PLATYCRINUS Jliller. 



Platycrimis verrucosus (n. s.) Body of medium size, 

 deeply cup-shaped, about as high as wide ; base broadly 

 convex ; facet for the attachment of the column moderately 

 large and circular, or subcircular ; first radials higher than 

 wide ; articulating facets of the arms shallow, wider than 

 high, occupying about half the width of each first radial 

 plate ; second radials very small, not occupying the full 

 width of the facets, the arms bifurcating immediately upon 

 this, with only one plate intervening between the first, and 

 each of all the other bifurcations. Arms moderately large 

 and long, composed of a double series of joints; tentacula 

 numerous and strong. 



Surface marked by somewhat scattered, prominent, 

 wart-like nodes, elevated abruptly from the surface of 

 the plates, sometimes coalescing, and having a tendency to 

 arrange themselves in rows parallel to the sutures, and on 

 the first radials a part of them being often arranged in two 

 rows, diverging from the base of the arms to each of their 

 lower angles. The arm-plates between the first and last 

 bifurcations are somewhat tumid, but the arms them- 

 selves are without ornamentation, except fine granulation. 

 Column subcircular at the top, but rapidly increasing in 

 size from the body, assuming a twisted oval shape. This 

 species has been referred to P. Yandelli of Owen and 



