ECHINODERMATA OF THE BRASSFIELD FORMATION 
31 
In the case of ray I, what is regarded as the ambulacral groove 
is overarched, at least proximally, by a number of small plates 
not seen on the other rays. The outlines of only a few of these 
small plates can be distinguished, and these do not suggest any 
analogy with the ambulacral and adambulacral plates among 
the Asteroidea. The arching plates, except at the proximal end 
of the ray, appear to be thin, and appear to sag readily into the 
ambulacral groove. Similar over-arching plates may have ex- 
isted formerly over the proximal ends of the ambulacral grooves 
of all of the other rays, but, in the present worn condition of the 
specimen no trace of these plates can be detected. The proximal 
half of ray III at present shows no trace of the ambulacral groove, 
probably on account of weathering, but the longitudinal de- 
pression formed by this groove is retained on the distal half of 
the ray, and here the short vertical pores already described occur 
along the central part of this depression. 
Locality and position. Associated with Dimer ocrinus (?) 
vagans, within 2| feet from the top of the Brassfield limestone, 
at a locality reached by going from Byron, Ohio, 1 mile east and 
then 1 mile southeast. The exposure occurs in a shallow wet- 
weather stream bed, east of the road. In a direct line this ex- 
posure is less than seven miles northwest of Xenia. 
Remarks. The affinities of this species among the Echinoder- 
mata are highly problematical. The arm structure does not 
resemble even remotely that of the Ophiuroidea or Auluroidea. 
The entire absence of any structure resembling ambulacrals and 
adambulacrals excludes it from the Asteroidea, even from the 
Cryptozonia division of the Asteroidea. The specimen here 
figured and described is the only one found in many years of 
collecting, and there seems no prospect of securing additional 
illuminative material in the near future; hence its present 
publication. 
The excellent photographs forming the basis of the accompa- 
nying figures were prepared by Dr. Herrick E. Wilson, of the 
U. S. National Museum. 
