LYON—BLASTOIDEBA. 629 
the central axis from the lower part of the fork to the sum- 
mit, obliquely truncated for the reception of the interradial 
pieces. Jnterradial pieces five, triangular small, short, and 
for their length very broad. Pseudambulacral fields five, 
broad, diminishing by a curved line on either side from above 
downwards, acutely pointed below, filling the fork and rising 
nearly as high as the radial and interradial pieces at their 
margin, less than half the length of the specimen; the poral 
pieces filling these fields, thin; about 100 measuring an inch, 
from 38 to 39 in either side of each field in the specimen fig- 
ured, separated by a slight but well defined line in the mid- 
dle of each field; the line separating either side of the fields 
into two divisions, is only visible by the aid of a good lens. 
Ovarian openings five; four of the pseudambulacral fields 
terminate at a minute circular opening, the other field termi- 
nating at an ovoid opening about four times as large as either 
of the others. This last opening occupies the summit of the 
field, the first to the right hand above the imperfect first ra- 
on. Mouth small, central, at the summit irregularly stelli- 
orm 
Surface markings, if any, obliterated by the mineralization 
of the specimen ; it is silicified. 
The general form of P. calycinus approaches that, of P. 
DP Orbignyanus de Koninck, and belongs to Reemer's division 
florealis. 
Geological position and Locality—A single entire speci 
men and two fragments were procured from the upper bw 
of the second limestone of the Millstone-grit beds, near os 
ridge’s ferry in Grayson County, Ky. It is not pe > 
that its horizon is in the third limestone of the beds allude 
to; no specimen or fragment of one could be seen in place in 
either bed, It must be very rare. 
Size of the Specimen.—Length of specim 
greatest eisiiatiet ah’s 3 ms length of _pseudambulacral 
areas, $3", ; greatest length of first radial pieces, Ts ; Lt is 
est “is of second radial pieces, fis ; Sarg iy 
asal pieces, +°.; leneth of interradial pleces, joo: 
drawing represents the specimen a little too full at the base 
of the pseudambulacral areas. 
en, 7¢s inches ; 
PENTREMITES ROBUSTUS, Nl. SP- 
(Plate XX., Fig. 2a, 2b, 2c.) 
Body symmetrical, ovoid above the lower eo aw 
dambulacral fields; contracting suddenly from t cs 
upper margin of the first radials. Basal a sie | 
minute ; perforation small, round. J’irst raduars meer: 
compared with the rest of the body, centrally pro ’ 
