Echinoid Radioles, AnnuJocidciiis. 
169 
Actual length . . 
Greatest width . . . 
Thickness across blade 
Thickness in'median line 
Thickness along #— y . 
13'4 mm 
17'9 * 
1*3 » 
0'9 » 
1*1 » 
In general appearance and thinness it reminds one of A. testudo, but the size 
is rather large for that species, and the excavation (30 per cent of the thickness) 
is more appropriate to A. Buchi. 
Probably both these radioles from the Cardita Schichten represent a species 
descended from A. Buchi and not so different from it as is A. testudo. More 
specimens are needed to settle the matter. 
Nature and relations of the Radioles in Anaulocidaris. — In 
attempting an explanation of the peculiar shapes of these radioles, comparisons have 
been made with two living echinoids. Benecke (1884) was the first to compare 
the trulliform radioles with the large radioles that in the recent Echinometrid Colobo- 
centrotus atratus form a sort of tesselated pavement over all the upper half of the 
test. Doederlein (1886) compared the paletiform radioles with the «schildförmigen 
Stacheln» which in Goniocidaris clypeata «bilden ein förmliches fast geschlossenes 
Dach über der Apicalfiäche des Seeigels». The complete series of radioles from 
Bakony for the first time permits of an exact comparison and reconstruction. 
The radioles in question are all primary radioles, borne, as was correctly 
supposed, by the main interambulacral tubercles of a Cidarid. Over the greater 
part of the test no other radioles of any importance could have found place, and 
the plates of the test (if correctly referred to this genus) prove in fact that no other 
radioles were borne by the interambulacrals. 
The Radioli remiformes were, one must suppose, confined to the adoral surface 
of the test, where they probably served chiefly for locomotion. 
The Radioli spatuliformes clothed the succeeding infra-ambital region. The 
blades were directed downwards, and the blade of each overlapped the handle and 
part of the blade of a radiole below. Owing to the alternation of the interambulacrals 
and of their tubercles, these radioles also must have alternated, and must thus have 
been arranged like the scales of a fish. They were not, however, closely pressed 
to the corona, but spread outwards, and formed a kind of frill round the base of 
the urchin. 
The Radioli trulliformes protected the greater part of the supra-ambital region. 
They alternated and overlapped in the sarne way as the spatuliformes, the N. margin 
being adoral, but the overlapping was confined to the bevels. Their hexagonal 
outline shows that no gaps were left in this outer covering. This close juxta- 
position of the blades prevented lateral motion of the radioles, but they could be 
slightly depressed, without, however, losing contact. Hence the transverse exten- 
sion of the acetabulum and tubercle. 
Allusion has been made to a slight asymmetry in the spatuliform radioles of 
A. Buchi by Laube, and in the trulliform radioles by Benecke. Similar asymmetry 
is sometimes noticeable in A. testudo. In so far as this has any meaning, it may 
perhaps be due to the probable fact that these radioles, though borne only by 
