72 
The plates termed ambulacral by Do Koninck are in reality the adam- 
biilacral, the ambulacral elements being contained in the ray avenues ; but the 
tubercle-bearing auxiliary plates mentioned in bis description I have not seen. 
The only specimen showing the actinial surface is mucb destroyed, 
and docs not display this portion distinctly. In De Koninck’s figure of this 
aspect of the body the oral plates each appear to be composed of two small, 
rounded, tnbercle-like halves. The disc, when viewed from the abactinial 
side, is seen to be prominent and straigbt-walled externally, either flat or 
concave on its upjier surface, with five node-like projections answering to 
each median interradial line. 
The madre^Joriform plate has been seen in two examples. It is a large 
oval piece, placed on the steep wall of the disc, and lietween two rays in the 
usual manner, with the component radiating laminae distinctly visible. 
In one specimen the arms are Iavo and fonr-eigbtbs inches long, and 
in another example one and fivc-eigbtbs inches long from the centre of the 
body. 
I have not seen an ambnlacrum with the plates in situ, but De 
Koninck’s figure {Loc. cit., PI. VII, Pig. Qf) represents them as opposite, a 
character which, if correct, Avould not only remove the species from FaUnaster, 
but also from the Encrinasteriae. 
Very fcAv Carboniferous species of Palccaster have been described. 
One has been figured ^ by Prof. Traiitscbold from the ILussian Carboniferous 
Limestone as Palccaster moutanus, Stseburovsky, sp., but the size and general 
proportions are so different to onrs that the comparison need not be carried 
further. Mr. S. A. Miller has also described a Palccaster from the Keokuk 
Group of the Americin Sub-Carboniferous System, under the name of P. 
crawfordsvillensis-, but the description is not Avitbin my reach. 
CrihelUtes carhonarlus, G. Tate ^ the Carboniferous Limestone species 
met with in Nortbumberland (England) is also a small form, Avitb rays only 
1’5 inch in length. The rays are rounded and lanceolate, Avitli the dorsal 
surface covered Avitb tubercles. 
' Kalkbruche von Aljatsclikowa, Pt, 3, 1879, p. 9, t. 2, f, 2a anil h. 
- Journ. Cincinnati Soc. Nat. Hist., 1880, \l(fde S. A. Miller). 
^Report Brit. Assoc. Adv. Sci. for 18C3 [18G4], Pt. 2, p. 88. 
