222 
The Ohio Naturalist. [Vol. XIV, No. 3, 
There are 39 ambulacral plates on one half-arm and 29 on the 
other. The adambulacral plates, sometimes called the inter- 
ambulacrals, alternate with the ambulacral plates. There are 
forty of these on the one arm and twenty-seven on the other. The 
skeleton is complete along the whole of the inter-ray in which the 
madreporite lies except for the rows of the movable spines which 
were based on the adambulacral plates. 
Fig. 1. Promo-palaeaster dyeri Meek (?). Natural size, dorsal view 
part of disc and arms. 
There are a number of starfishes described in the publications of 
the Ohio Geological Survey. Of these Palaeaster dyeri Meek, 
(Plate 4 Vol. 1 part 2 of the Palaeontology) resembles most closely 
the starfish under discussion. The specimen there figured was 
of a larger animal than this one but as Professor Meek says in his 
introductory statement, the poor preservation of the parts leaves 
much to be desired in the description. 
The madreporite of P. dyeri is trilobate. Its shortest dimen¬ 
sion is in the inter-ray and its longest at right angles to this in the 
horizontal plane. These dimensions are (> m. m. vertically and 
9 m. m. horizontally. 
The madreporic body of my specimen shows a trace of this 
lobation only. The vertical plane dimension is 7 m. m. while the 
horizontal diameter is 0 m. m. It has quite a different general 
shape then from the madreporite of P. dyeri but the size is almost 
the same relatively, in view of the sizes of the animals. The 
appearance of the canals on the surface of the two madreporic 
bodies is very similar, though the pattern of the lines differs with 
the shape of the bodies. 
