150 
Triassic Echinoderms of Bakony. 
does surprise one is that the striae which radiate from the handle over the inner 
face to the SE. and SW. margins do, in like manner, pass over those margins, 
and then continue over their bevels on the outer face in a direction parallel to the 
NE. and NW. margins, until they meet the striae passing from the S. margin to 
those margins. What happens next is not clearly shovvn in specimen /, for there, 
as in most, the striae are not distinct except near the margins. From a few other 
specimens, in various States of preservation, it appears that the striae parallel to 
the NE. and NW. margins continue across the radiating striae; or, rather, the 
structures merge in a regulär manner and initiate a series of concentric ridges 
parallel to the NW., N., and NE. margins. 
Inner face. Outer face. 
Text-fig. 18. Anaulocidaris testudo. 
Diagrams of trulliform radiole, to show direction of lines of Ornament. The lines are put in more 
closely between a, b and c, d, and the same lines may be traced from the inner face, over the edge 
to the outer face. 
The passage of striae from the inner to the outer face over the SE. and SW. 
margins, as well as over the S. margin, appears to indicate that all those tracts 
of the inner face, to the S. of lines drawn from the acetabulum to the NNE. and 
NNW. corners, are morphologieally part of the outer face. The broad ridges that 
were described above as passing from the handle to the E and W. corners may 
thus be the obsolescent remains of the original margin of the remiform radiole. 
But, however it may have arisen, this passage of the striae has produced tvvo 
strongly contrasted patterns on the two faces of the blade; and, since the striae 
arise out of the intimate structure of the stereom, it results that one face is built 
on a different plan from the other. This is not perhaps what one would naturally 
expect in so thin a blade, but it is rendered possible by the well-known structure 
of the Cidaroid radiole, with its ostracum or epistereom. In these blades the 
mesostereom is very thin, or even absent, towards the margins, but the epistereom 
of each face remains distinct from that of the other face, as may be seen in some 
broken specimens. 
Having described specimen / as typical of the trulliform radioles, we may 
now proceed to the measurements of the 19 radioles selected to show the gradual 
modification within the limits ot this form. In the following figures the outer or 
adapical face is shown in a, b, c; in all the others the inner face only is represented. 
The specimens have been arranged so as to illustrate the continuous series 
that connects the radioli spatuliformes with the paletiformes. The feature by which 
one is chiefly guided is the gradual bending of the handle, and its passage from 
the S. margin towards the centre of the blade, since this appears to be the feature 
