3o8 American Geologist. ^^^y- i»o» 
This is the rarest blastoid in the Boonville beds and the 
specimen figiired is the only plump one the writer has seen. 
Of four other specimens in the collection, all are much larger 
than this one but crushed out of shape. The test seems to be 
very thin. 
There is some doubt about the correctness of this reference, 
since M. kirkzvoodensis comes from a higher formation, the St. 
Louis limestone. Also, our specimens are less concave at the 
ventral or top end, but otherwise agree fairly well with Dr. 
Shumard's species. 
In the Boonville beds there is a strong commingling of 
Keokuk and Warsaw fossils. 
Keokuk- Warsaw limestone, Boonville, Mo. 
Codaster superbus, n. sp. 
Fig. 35. A natural chert cast of the visceral cavity of the type 
specimen, side view. 
Fig. 36. Ventral view of the same specimen showing the hydrospire 
slits, ambulacra and other features. 
The basal plates are quite half the body in length and form 
a pyramidal cup. 
The radials extend to the ventral surface, the interradials 
being very small and not visible on a side view. 
The very narrow ambulacra are short and occupy the bot- 
tom of rather deep valleys whose sides are crossed by fifteen 
or sixteen hydrospire slits each or from thirty to thirty-two to 
the area. 
These slits are crowded, parallel with each other and the 
ambulacrum. 
As in Codaster grandis, the slits occupy both sides of 
ever\' inter-ambulacral area, thus excluding both these species 
from the genus Codaster as rediagnosed by Ethbridge and Car- 
penter. 
The anal opening is not large and the central area, usually 
open in most species of blastoids from the fragile character of 
the covering plates, is closed in this specimen. 
As in other species of the genus, the ornamentation is fine 
lines parallel with the plate sutures. The stem was small and 
the perforation minute. The type came from a piece of chert 
not in place but, from associated fossils, evidently belongs to 
