FROM TITE PALAEOZOIC ROCKS OF INDIANA, KENTUCKY AND OHIO. 463 



the proboscis, arc ornamented by three or more hemispherical tubercles, differing in size, 

 irregularly disposed across the pieces. All the other pieces of the dome arc gibbous or 

 concave, and not ornamented. In better preserved specimens, it is probable that the whole 

 surface of the dome will be found covered with fine granules. 



All the pieces of the body below the arms are covered with fine ridges, disposed in 

 groups, radiating from the centre of the pieces; on the radials, and larger pieces, these 

 number from six to ten in each group; thus the margins of the first interradials arc orna- 

 mented by about seventy of these ridges. Column and arms unknown. 



Size of Specimen. 



INCHES. 



Eeight of body below the arm-bases, 3G 



Eeight of dome to base of proboscis, 67 



Eeight of whole body, 1.03 



Diameter of calyx at arm-bases, .- 1.37 



Diameter of base of proboscis, 46 



Diameter of basal pit, ..... ..... .30 



Locality and Geological Position. — Nucleocrinus bod, or lower crinoid bed, Falls of the Obio, Clark 

 County, Indiana. Very rare. The specimen figured is of an adult, unusually largo for tins species. 



A few years ago a crinoidal body was received in exchange, from a friend, having a 

 label attached, "Collected near Dayton, Ohio." 



This fossil attracted considerable attention ; its anomalous structure, and general appear- 

 ance, separated it from all crinoids that had come under my observation. 



In the year I860 a drawing was made of it, preparatory to description. The troubled 

 condition of the country at the time, and during the. war, delayed the paper describing it. 

 I now propose a description of it, and to erect a new genus for its reception, and other 

 similar forms, under the name of Ataxiacrinus (Jrafte), irregular ; and the following generic 

 formula is submitted. 



Ataxiacrinus, n. g. 



Generic Formula. 



Basal pieces, 5. 



Eadial pieces of the first series in throe rays, 1 to each ray to the free arms. 



Radial pioccs of the first scries in two rays, 2 to the free rays. 



Supplementary radials to the rays with two radials, 1. 



All the free rays, and supplementary radials, arm-bearing. 



.Dome covered by many small pieces. 



Anal pieces. (?) 



Column subpentagonal ; opening pentelobate. 



Arms unknown. 



