184 FAL^EONTOLOGY OF ILLINOIS. 



radial; and its left side connects with another anal piece, rest- 

 ing upon the truncated upper end of one of the sub-radial pieces. 

 On the truncated upper margins of these two anal pieces two 

 others are supported, but our specimen is not in a condition to 

 show their form, or to enable us to determine whether or not 

 they are succeeded by any other anal pieces above. 



The arms are all long, robust and rounded, those of the 

 two posterior, and the two lateral rays, after the first bifurca- 

 tion on the third radial piece, bifurcate again on the ninth 

 piece, beyond which they seem to be simple, and are each com- 

 posed of a single series of short, somewhat wedge-shaped joints. 

 The column is composed, near the body, of firmly anchylosed 

 segments, the sutures of which are not visible 0.20 inch below 

 its connection with the base. Its central cavity presents in a 

 transverse section, the same pentapetalous form seen in the 

 central perforation of the base. Length to summit of third 

 radial pieces, 0.86 inch; breadth at the summit of the first 

 radial pieces, about 0.60 inch. 



Fig. 3. 

 This species seems to be 

 more nearly allied to Poteriocri- 

 nus missouriensis, of Shuinard, 

 than to any other with which 

 we are acquainted. It differs, 



however, in having a less grad- ^\ t — v^T— ^ 



ually tapering body (though the 

 specimen we have figured is com- 

 pressed so as to give its body a 

 broader appearance than is nat- 

 ural), and much stronger arms, 

 which differ entirely in their 

 mode of branching, as well as 

 in the form of their segments. 

 Our species has also a propor- 

 tionally smaller column at* its n . PoUriocrinusSwallovi. 



J Diagram of body and rays to the bifurcation on the third 



junction with the base. It Was radial pieces. Natural size. 



• named in honor of Prof. G. C. Swallow, State Geologist of Kansas. 

 Locality and position: Same as preceding. 



9>c, 



°R9P.. 



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