378 PALAEONTOLOGY OF ILLINOIS. 



In one specimen, however, agreeing exactly in other 

 respects, the third radials in the anterior and one in the 

 posterior rays is immediately succeeded by brachial pieces 

 without any further bifurcations, so as to give origin to 

 only two arms to each of these rays; but this is almost cer- 

 tainly an individual abnormal development. 



Eirst anal plate a little longer, but not otherwise differ- 

 ing from the first radials ; above this there are three smaller 

 pieces in the next range, and sometimes one or two still 

 smaller ones in the third range. Interradial pieces one to 

 three in each space, the first being one-third to one-half as 

 large as the first radials, seven to nine sided, and usually 

 supporting one or two smaller pieces in the second range 

 above. 



Vault convex, and composed of very unequal, irregular, 

 moderately convex plates, provided with a tube or probos- 

 cis of moderate thickness, and placed generally about half 

 way between the middle and the anal side. (Column and 

 arms unknown.) 



Hight to base of proboscis, about 0.58 inch ; do. to arm 

 openings, 0.33 inch; breadth, 0.55 inch. The specimen pre- 

 senting the irregularity mentioned in the arrangement of 

 the arms, is proportionally wider than that from which the 

 above measurements were taken. 



This little species is apparently nearer B. clio, Hall, (sp.), than to any 

 other yet described. Its base, however, is much less thickened and 

 expanded than in that species, and its body-plates more even and smooth- 

 er ; while its brachial pieces are less prominent, so as to give its body 

 a less spreading appearance. Judging from the description, the B. laura, 

 Hall, (sp.), would seem to be somewhat like our species, but that form 

 must be more depressed and proportionally wider, and is also said to 

 have the arm openings directed upward, which would even place it in a 

 different section of the genus. 



We place this species provisionally in the Eretmocrinus group, from 

 its general appearance, as we have not seen any specimens showing the 

 arms. 



Locality and position Lower division Burlington group of Lower 



