214 Triassic Echinoderms of Bakony. 
varies from 02 to 0°4 mm., the latter height being attained only at the proximal 
end. Ribs broken up into (or formed of coalesced) pustules; these are larger 
and more discrete at the proximal end of the shaft, where four occupy a length 
of 24 mm.; about the middle of the shaft five occupy the same length. 
Base occupies about 0°38 length of radiole, this high proportion being due 
to the collerette, which measures 5°8 mm., and is bounded distally by a slight but 
distinct rounded rim, partly formed by the proximal pustules of the shaft. This 
rim, although equidistant from the annulus, is not at right angles to the main radiole- 
axis, but slopes distalwards to that face of the shaft on which the ribs are the 
more distinct. With this rim the annulus and acetabular margin are parallel. Least 
diameter of collerette (dorsoventral, 2°2 mm.; transverse, 2°3 mm.) at one-quarter 
of its length from the annulus; thence the collerette swells to 2°8 and 3 mm. at 
the distal end, and 2°6 mm. next the annulus. The curve produced by this swelling 
is more concave on that face which has the more distinct shaft-ribs; thus the 
main radiole axis is slightly bent towards that face. Surface of collerette marked 
with linear striae, 25 to the millimetre; these represent the outcropping edges of 
regularly radiate septa, and regularly spaced trabeculae are seen between them. 
Annulus rounded, separated by a clear step from the collerette, but passing 
gradually into the slope of the base Diameter 3 mm., height about O06 mm. 
Longitudinal striae of the same size, but more clearly marked, pass directly from 
the collerette over the annulus, and die out on the slope of the base, which is 
straight or faintly convex. 
Acetabular margin circular, prominent, slightly curved downwards dorso-ventrally, 
and coarsely crenelate, with an outer diameter of 2,1 mm From the margin the 
sides of the acetabulum gently shelve inwards, and then suddenly bend down to 
form a pit with vertical sides and a diameter of 0°85 mm. Total depth of ace- 
tabulum 0°77 mm. 
The micro-structure may be inferred to some extent from the study of 
the surface. In the region of the collerette there would doubtless be an outer layer, 
probably extending to an axial complex or lumen, composed of regular radiate septa 
with regular trabeculae. In the grooves of the shaft the vertical edges of the out- 
cropping septa are seen to wave, dichotomise, and anastomose, at irregular intervals, 
and about 15 occupy half a millimetre (fig. 397). The trabeculae are often arched 
convexly upwards. It may therefore be supposed that in this region a transverse 
section would show similarly irregular and waving radiate septa with an irregular 
meshwork. 
The Characters of the Species. — The lectotype was the only 
specimen known to ScuarHAuTL, and appears to form the sole basis of WonrMaNN’s 
description, though some other specimens or fragments must have been known to 
him. These facts, as well as its excellent preservation, may lead one to exaggerate the 
importance of this single specimen, and to regard as diagnostic of the species 
characters that may be merely individual. For example, the variation in length of 
collerette observed in some other species should make one hesitate to regard its 
unusual length in the lectotype as a necessary character. The number of ridges 
certainly must be expected to vary with the size of the radiole, and even in the 
lectotype it is not so precise as at first appears. The constitution of the ribs may 
also be expected to vary: the incipient ridges of the lectotype are formed of isolated 
