80 
Triassic Echinoderms of Bakony. 
Description o f t h e Specimens. — The plates are all thin in proportion 
to their area, but not remarkably so. The fragments a and b are clearly adoral; 
and that the remaining plates also are from either the adoral or adapical regions, 
is proved by the angle vvhich the adradial margin forms with the two parallel 
tranverse margins, as well as by the marked inequality of the orad and apicad 
interradial margins. The slight differences between the specimens are due partly to 
their having come from different regions of the interambulacrum, partly perhaps to 
their derivation from individuals in different stages of growth. 
Fragment a (fig. 141) contains in its a column 3 well-developed main tubercles, 
which rather rapidly increase in size avvay from the peristome, also apparently a very 
small obsolescent tubercle on the peristomial border; its b column shows 2 well-deve¬ 
loped tubercles, while a third probably underlies a detached plate that covers the adoral 
end of this column. The 6 or 7 plates that bear these tubercles form a piece of 
test in which no sutures can be distinguished even with the aid of Loven’s fluid, 
while the adapical edges are fractured and correspond with the assumed Position 
of the sutures for only a small distance. This adoral region of the interambulacrum 
is almost flat, but the wide interradial tract is slightly depressed, while the adradial 
tracts slope ge nt ly to the adradial margin. 
In specimen b (fig. 149) the union of the plates, though firm, was not so close 
as in a, for their outlines are clearly indicated by depressed sutures, and the 
boundary of the fragment to a large extent corresponds with the sutural edge of 
an interambulacral. 
Specimens e and f afford further proof that the transverse sutures of the 
interambulacrum were not flexible. At the same time a slight bevel can be detected 
when the margin is well preserved. Thus in e the free margin of the smaller plate has 
a slight bevel facing outwards (fig. 145), and this is carried round the adjacent 
limb of the interradial margin, which is the smaller limb ; the free margin of the 
larger plate has a bevel facing inwards (fig. 146), but it is not conspicuous, partly 
because the margin is a little worn. Although these bevels are so slight that 
they might rather be described as a slight deviation of the suture-face .from the 
vertical, still they are enough to suggest that, in accordance with the general rule 
of adapical imbrication, the smaller plate is adoral, and consequently that the 
fragment comes from the adoral region. In the isolated plate c, the shorter, i. e. 
the adpolar, of the transverse suture-faces is slightly grooved, while the longer, 
adambital one shows no definite bevel; if the grooved margin be rightly regarded 
as adapical, then this plate is from the adapical region. 
The position of the main tubercles on the interambulacrals varies with regard 
to both the adradial and the adapical margins. Taking the first point, we note that 
in a, if the transverse diameter of each plate be taken as 100, then the distance 
of the centre of the tubercle from the adradial margin is, in the adoral plate, 42, 
in the next, 38, and in the next, 37. In both e and f, which agree fairly well in 
size and probable position with the second and third plates of a, the corresponding 
ratios are about 47 and 41. From these facts it follows that, in the strictly adoral 
region, the tubercles assume a more adradial position according as the plates are 
remote from the peristome. Possibly this tendency continued to the ambitus, but 
in c the ratio is 50, and this suggests that in the adapical region the tubercles became 
more central. In spite of the ratios, the line of tubercles appears to approach the 
