Beede.] Carboniferous Invertebrates. 41 



" The subradials [basals] are very large, extending into the 

 basal cavity, and curve gently upward: three hexagonal, 

 the two longer sides unite with the subradials ; the two up- 

 per sloping sides, uniting with the first radials, are a little 

 shorter, and the two under sides, uniting with the basals 

 |infrabasals] are very short; two are heptagonal, the one on 

 the right of the first azygous plate being much larger, and, ex- 

 cept the two short sides uniting with the basals, the other sides 

 are of subequal length; the one upon the left has, in addition 

 to the two short sides uniting with the basals, a short side unit- 

 ing with the second azygous plate. Four of the first radials are 

 pentagonal, twice as wide as high; the upper face is the full 

 width of the plates, and projects over the interior of the calyx so 

 as to give the appearance of having great thickness when viewed 

 from above. The other first radial, upon the right of the azygous 

 plates, is quadrilateral, except a very slight truncation by the 

 second azygous plate below the depth of the suture. The first 

 radial is separated from the second or brachial piece, on the 

 outer face, by a wide suture, but within a crenated ridge ex- 

 tends from one angle of the plates to another, forming a penta- 

 gon, except as separated by the second azygous plate ; the ridge 

 has a furrow upon the outer side in the central part of each 

 plate, and within this is a wide expansion which supports the 

 brachial arm pieces. The first azygous plate has four sides, 

 rests between the upper sloping sides of the two subradials and 

 along the under side of the first radial on the right, with the 

 shorter side abutting on the second azygous plate. The second 

 azygous plate is hexagonal, curves inward, and supports upon 

 it- two short inner faces the third and fourth azygous plates, 

 side by side. The vault and other parts unknown." In our 

 specimen the right posterior radial seems to be covered by one 

 of the plates of the ventral sac. 



Range and distribution : Upper ( 'oal Measures ; Kansas City. 



4 — vi 



