126 PALAEONTOLOGY OF OHIO. 



range gradually decreasing in size upwards. Anal area larger than the 

 interradials ; the first plate large, usually supporting three in the second 

 range, above which they are not so regularly disposed, and gradually de- 

 crease in size. The constriction between the arm bases on the anal side 

 is much larger and deeper than those of the interradial areas. 



The dome appears to have been composed of a large number of small 

 polygonal plates, without any definite arrangement or order. The arm 

 bases are small, indicating slender arms, their structure and form un- 

 known. As the specimens consist only of internal casts of the body, the 

 surface features of the plates have not been observed, as no parts of the 

 matrix has been preserved in collecting. 



The general form of the body and plates corresponds exactly with the 

 form in Dr. Troost's collection, and with the figures and MS. description 

 of his Actinocrinus Tennesseensis. The form described as A. (Sac.) Christyi, 

 Hail, is more spreading towards the top of the cup, but the dome of that 

 species is seldom preserved ; the other features correspond more nearly 

 in the two forms. 



Formation and locality : In the limestones of the Niagara group, at Yellow Spiings, 

 Ohio. Collection of Prof. Edward Orton. 



Saccocrinus ornatus (n. sp.). 



Plate 6, fig. 7-9. 



Body of medium size, obovate, or elongate urn shaped below the arm 

 bases; obscurely pentangular in the upper part of the cup, from the flat- 

 tening of the interradial areas ; the body surmounted by a long, very 

 slender proboscis. Basal plates of moderate size, forming about as much 

 of the height of the cup as the width of one of the plates. Plates of the 

 radial series elongate, the first ones much larger than any others in the 

 body; second and third about of equal size, but differing slightly in 

 different rays ; the third plate is obtusely cuneate above, and suj^ports 

 two sub-radials on each side, one above the other, the first being about 

 two-thirds as large as the third radial, the other about half as large 

 as the first, and supports the free arms, one on each division of the ray, 

 giving ten arms only to the body at the margin of the cui3. Between 

 the second supraradials there is a single small intersupraradial to each 

 division. The interradial series consists of a single first interradial 

 plate, which is about equal in bi;e to the second radials, hexagonal in 

 form, and supporting two plates in t.-o second, third, and fourth ranges, 

 with sometimes one, two, or three very small ones in the fifth, high up 



