Triassic Echinoderms of Ba.kony. 
104 
.4. testudo it exceeds 200: 100 in nearly all the specimens and in k and r reaches 
234 and 246:100 respectively, or 256:100 if the blade alone be considered. 
ln the remiform and spatuliform radioles, the blade appeared relatively thicker 
in A. Buchi, but it was not found possible to prove this by measurement. ln the 
trulliform radioles more exact comparison is possible and proves the relative tenuity 
of A. testudo. This is best seen by taking the ratio of thickness in the middle line 
at the equator to the length of the blade, and especially by selecting for comparison 
radioles of about the same shape. Thus in A. Buchi BM,/, this ratio is 0*211, 
while in A. testudo g it is 0174 and in k it is 0T26. Again in A. Buclii BM, g, 
the ratio is 0'217, while in A. testudo h it is 0T47, and in s, 0'139. 
If the measurements right across the blade or along #— y be compared, the 
relative thickness of A. Buchi is still greater owing to the presence of the ridges. 
These, which are almost imperceptible or entirely absent in .4. testudo, are always 
obvious in A. Buchi. In the words of Benecke, «Auf der einen Fläche [i. e. the 
inner face] zwei ganz stumpfe Kanten von dem Kegel nach den distalen Ecken 
laufen und die eine Fläche des Radiolus daher .... in drei Felder zerfällt.» 
The trulliform radiole f, a normal example of A. testudo, may be compared 
with Benecke’s excellent description of the corresponding radiole in A. Buchi and 
with the British Museum specimens (/, g, h). 
First, as to outline. Benecke describes and flgures the proximal margin as a 
continuous curve. The SW. and SE. sides seen in A. testudo are not distinct from 
the S. side in A. Buchi. Benecke’s further Statement that this curve bends round 
and joins the distal (N.) margin in a curved line is applicable to BM, f, but not 
entirely so to BM, g, and h, since in both of these distinct NW. and NE. sides are 
developed. In BM, h, the extreme length and straightness of those sides is to some 
extent due to fracture, and that is how Benecke explains other cases. This, how- 
ever, is certainly not the case with the NW. side of BM, g, as seen from the outer 
face; and signs of bevelling lead to the inference that there were distinct NW. 
and NE. sides in h also. 
Benecke says: «der distale Rand des Radiolus ist gerade». This, were it so, 
would constitute another difference from A. testudo; but Benecke's own fig. 1 
shows a distal margin with a sinuous outline similar to that above described for 
A. testudo , though the curves are perhaps not so marked. There was apparently 
a similar curve in BM, h ; but in BM, g, the distal margin has an almost imper¬ 
ceptible concavity, whereas in BA4, f, it is slightly convex This uncertainty of outline 
in A. Buchi is in contrast with the marked double curve seen- in all trulliform 
radioles of A. testudo, though sometimes more and sometimes less marked than in 
specimen /. 
Next, as to the form of the outeiyface. Benecke’s description of it as «etwas 
wellig gebogen» lacks precision. It is somewhat regularly convex in BM, / and g; 
but in BM, h there is a median depression, similar to that described in .4. testudo 
but more marked. 
As regards the proximal margin, presumably of the outer face, Benecke says 
that it has, «nach seinem Aussehen zu urteilen, einem anderen Radiolus zur Unter¬ 
lage gedient». Probably he is referring to a distinct slope or bevel of this margin, 
though he does not describe any such. This bevel exists in BM, g and h, but, 
since it approaches the slope of the whole surface more nearly than in A. testudo, 
