762 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



Radials a little longer than wide ; the lower faces moderately convex ; the 

 lateral ones parallel ; the upper nearly straight, not sloped at the outer ends 

 and but little impressed at the facet, which is narrow and somewhat thick- 

 ened around the margin. Anal plate generally wider at the lower end than 

 the radials, and one fourth narrower at the top ; its lower face obtusely 

 angular. All parts above the radials unknown. Column round and small. 



Horison and Locality. — Lower Burlington limestone, Burlington, Iowa. 



Type in the Museum of Comparative Zoology. 



Dichocrinus ornatus W. and Sp. 

 Plate LXXYIL Fig. 6. 



1881. Bichocnims ornatus — W. and Sp. ; Revision Palseocr., Part II., p. 84. 



Sjn. Dichocriims scnlptus — Cassedat and Lion (not De Kooinck and Le Hon, 1853); Proceed. 

 Amer. Acad. Arts and Sci., Vol. V., p. 25. 



A very small species. Calyx to the top of the radials about as wide as 

 high ; regularly cup-shaped ; broadly truncated at the lower end ; the sides 

 a little convex; the npper margin slightly contracting. Plates covered 

 by conspicuous, irregular, undulating ridges, two of which descend from the 

 top of the dorsal cup to the foot of the basals, two others obliquely in the 

 direction of the lower lateral angles of the radials, touching slightly the 

 upper end of the basals, and two shorter ones pass out to the lateral faces of 

 the radials. 



Basal cup saucer-shaped, occupying two fifths the height of the calyx ; 

 the truncated lower face surrounded by a well defined undulating rim. 

 Radials a little longer than wide, widest at the top ; facets small and pro- 

 jecting outward. Anal plate almost as large as the radials, narrowest above. 

 Costals two, short; occupying less than one half the width of the radials. 

 Distichals two or three. Arms four to the ray, slender ; composed of long 

 cuneate joints which gradually interlock without being truly biserial. Pin- 

 nules long. The arms in most of the specimens are spread out horizontally. 

 Ventral disk low-convex ; anus directed laterally. Column round ; the nodal 

 joints projecting and provided with one or two long cirri. 



Horizon and Locality. — St. Louis group ; the type specimen in the 

 collection of Major S. S. Lyon came from Hardin County, Ky., that figured 

 by us from near Mt. Pleasant, Iowa. 



Remarks. — This is the smallest known species of Dichocrinus, and is 

 readily recognized by the spreading arms, long pinnules, and the striae 

 along the calyx plates. 



