INVERTEBRATES. 291 



Brachials pentagonal, about as long as the radials, compressed 

 laterally, so as to form a rather prominent ridge across the middle 

 of the plate, ending at the upper angle in a rather obtuse point. 

 All the body plates, including the second radials, are marked with 

 rugose striations directed from above downward to the base, giving 

 a rugose appearance to the surface of the body. The brachials are 

 sharply angular above, and support the first arm plates, which are 

 triangular, and one on each brachial is produced in front into a 

 little node that covers the projection at the summit of the brachial 

 plates. The succeeding arm plates are short, wedge-shaped, except 

 the axillary plates, which are longer than wide, and produced out- 

 wardly into an obtuse point. All the other plates of the arms, 

 where well preserved, show short spiniferous nodes on their outer 

 margins. 



The arms, after their first division on the brachials, divide again 

 on the eighth or tenth plate, and the outer division once or twice 

 more on the sixteenth to the twentieth plate, while the inner 

 branches continue single to their extremities. 



Column round, and near the top composed of short plates, the 

 alternate ones projecting beyond the others. 



Anal plates unknown. 



This species is evidently related to the crinoid figured by Yandell 

 and Shumard in their "Contributions to the G-eology of Kentucky," 

 without a description, but if their figure is correct, our speecis 

 differs from their "Cyathocrinus florealis," in the form and relative 

 proportion of the body plates, as well as in the bifurcations of the 

 arms. 



Position and locality: Chester limestone ; Monroe county, 111. 



No. 2,436, Illinois State collection. 



POTEKIOCEINUS SALTEBI, Worthen. 



PI. XXIX, Fig. 18. 



Poteriocrinus Salteri, WORTHEN, February, 1882. 



Bulletin No. 1. of the Illinois State Museum of Natural History, p. 21. 



Body small, basin-shaped, rather more than twice as wide as high. 

 Base depressed, and basal plates concealed in its concavity. 



Subradials about as long as wide, those on the anterior side 

 hexagonal, the lower angles curving into the basal depression, 

 protuberant and slightly depressed at their upper angles. 



