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ACROCRINIDAi W. and Sp. (1885). 
Monocyciic. BASALS SEPARATED FROM THE RADIALS BY A LARGE BELT OF ACCESSORY 
PIECES. RADIALS IN CONTACT EXCEPT AT THE POSTERIOR SIDE, WHERE THEY ARE 
SEPARATED BY AN ANAL PLATE, STRUCTURE OTHERWISE AS IN THE HEXACRINIDA. 
Geological and Geographical Distribution. 
Number of known species. 
FORMATION. ACROCRINUS. 
Carboniferous. Coal Measures. 
Kaskaskia group. 
Se Subcarboniferous. 
St. Louis group. 
Total species 
Ltemarks. — This family consists of the single genus Acrocrinus, which is 
only known from America, where three species have been found: one in 
each of the upper members of the Subcarboniferous, and one in the Coal 
Measures. It represents, therefore, the end of the Camerata, so far as our 
present knowlege goes. It appeared after all the other families were extinct, 
except a small remnant of the Platycrinide represented by a small but very 
prevalent species, and the Hexacrinide, from which its derivation is very 
apparent. It survived in the Carboniferous, from which a single very small 
specimen is known. 
In the interposition of accessory pieces between the primary plates of the 
calyx, the Acrocrinide approach the Reteocrinide; but the two families 
