Carboniferous Rocks of the Mississippi Valley. 321 



three plates ; above these the plates more properly belong 

 to the dome. Anal area similar to the interradial, except 

 that the first plate is truncated below, where it joins the 

 large sub-radial plate. 



Surface of plates smooth. Column round, very small, 

 abruptly expanding at its junction with the body, composed 

 of thin equal plates. The dome appears to have spread 

 laterally, so as to arch over the rays near the origin of the 

 free arms In medium-sized polygonal plates. The visceral 

 cavity has extended along the ray into the midst of the 

 armlet bases, which may have been covered by small 

 plates or by only a fleshy integument. 



This species offers in its general features a great depart- 

 ure from the characters of the typical form of the genus 

 Forbesiocrinus, but its three basal plates, five sub-radials, 

 and a radial series of four plates, correspond with this ge- 

 nus. The small patelloid plates are also traceable in some 

 parts of the radial series, and are usually quite distinct 

 among the plates of the arms. This species has the rays 

 more divergent than the Onychocrinus of Lyon and Cas- 

 seday, and its form is that of a stellate disc. In compar- 

 ing it with numerous other species of the genus, and with 

 that form described as Onychocrinus by Lyon and Casse- 

 day, I can see no sufficient reason for separating it from 

 Forbesiocrinus. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collections of C. A. WhitCy Rev. 

 W. H. Barris, and B. J. Hall. 



Mespilocrinus scitulus (n. s.). Body small, depressed- 

 subglobose, cup to the top of the first radials broadly sub- 

 turbinate, with slightly convex sides; base truncate and 

 sharply impressed ; the arras fold over each other on the 

 summit. Basal plates minute, having when united five 

 salient angles which extend for some distance between the 

 sub-radial plates ; the outer ends only of the basal plates 



JOURNAL B. S. N. H. 41 



