ECHINODERMATA OF THE BRASSFIELD (SILURIAN) 
FORMATION OF OHIO 
AUG. F. FOERSTE 
Relatively few echinoderms from the Upper or Albion di- 
vision of the Medinan Silurian have hitherto been described. 
From the Cataract strata of Ontario, Brockocystis clintonensis 
(Parks), Brockocystis huronensis (Billings), Brockocystis tecumseth 
(Billings), Mesopalaeaster (?) cataractensis Schuchert, and Meso- 
palaeaster granti (Spencer) are known. From the Girardeau 
of Missouri and Illinois, Cyclocystoides illinoisensis Miller and 
Gurley, Glyptocrinus (?) fimhriatus Shumard, and Ptychocrinus 
splendens (Miller) have been described. Deltacrinus alleni 
(Rowley), Gissocrinus (?) prohlematicus Rowley, Glyptocrinus 
inseparatus, with its varieties carinatus and pentagonus, all by 
Rowley, have been described from the Edgewood of Missouri 
and Illinois. 
Although the Brassfield formation of Ohio, Indiana, and Ken- 
tucky contains almost everywhere a considerable quantit of 
coarsely crinoidal material, only one species, Clidochirus ameri- 
canus Springer, has been listed by Bassler from this formation; 
even this species, so far, has not been published. 
This extreme poverty of echinoderm material from the Brass- 
field formation may be easily understood on studying the lithol- 
ogy of the rock. Where the echinoderm material is most 
abundant the rock gives evidence of having been deposited by 
strong and irregular currents. Cross-bedding is common. The 
fragmental material is more or less rounded. Dismembered 
plates and columnals of crinoids are common, fragments of col- 
umns an inch or more in length are not infrequent, but rarely 
are enough plates of the same calyx still found in their original 
relative position to make possible even a generic identification. 
The material described on the following pages represents all 
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