78 
Triassic Echinoderms ot Bakony. 
ance to T. subnobilis is so close that, with our present knowledge, the two cannot 
be separated generically. Unfortunately the systematic position of the latter species 
is itself uncertain, since it too is known only from interambulacrals. If, however, 
the choice is confined to Miocidaris and Triadocidaris , the latter is certainly pref- 
erable. Broadly speaking, T. praeternobilis continues the line of development repres- 
ented by T. persimilis, T. subsiniilis, T. Liagora, T. Suessi, and T. subnobilis ; it 
differs from T. subnobilis in the same way as that species differs from T. Suessi. 
The depression of the scrobicule, absent from the holotype of T. subnobilis, but 
observed in an unfigured paratype (electrotype in Brit. Mus., E 4798), is intensified 
in T. praeternobilis. The secondary tubercles with their perforated mamelons and 
manifest scrobicules are better developed in the present species, which is mainly 
distinguished by the regulär arrangement of secondaries and tertiaries; for in T. 
subnobilis no such regularity can be detected, while its secondaries and tertiaries, 
being relatively smaller, are also more numerous. These distinguishing features can 
be seen at a glance, even in a small fragment. In T. praeternobilis the platform 
of the primary tubercles appears to be less wide, and the parapet less sharply cut; 
but these are characters in which individual Variation must be allowed for. 
The two Bakony species of Triadocidaris come at the extreme ends of a 
continous series of which the intervening terms are found at St. Cassian. Since 
there is good reason to believe that T. praeternobilis occurs at a higher horizon 
than T. persimilis and higher than the St. Cassian beds, it affords some argument 
that the series, as previously described, is a truly progressive evolutionary series. 
Triadocidaris ?, cf. T. praeternobilis. 
(Plate VI. figs. 139, 140.) 
Material. —- Three small interambulacrals of peculiar appearance, found in the. 
Raiblian beds at Jeruzsalemhegy, and lettered a, b, c. 
D e s c r i p t i o n o f the Specimens. — The plates are all wider than high. 
c, the smallest of them, which is the most complete in outline appears hexagonal 
or heptagonal; probably it was essentialty of the ordinary pentagonal shape with 
the adradial angles rounded off, as is not unusual. a, when complete, must have 
appeared almost quadrangular, since the interradial margin, which is complete, is 
straight with only a slight truncation at one corner, probably the adambital; and 
this truncation is bevelled on the outside. The plates are thickened by an external 
ridge at the transverse sutures, which are approximately vertical and seem to show 
occasional traces of grooving. The straighter and longer portion of the interradial 
suture is also thick and vertical. The adradial margin appears to have been thinner, 
but presents no traces of definite bevels or denticles. 
The tubercle is best preserved in a. The mamelon is perforate, circular, 
depressed, not undercut, and of fair width relative to the diameter of the plate. It rests 
on a platform of nearly three times its diameter, with a low, broad, rounded parapet. 
In b and c the mamelon is broken away and the Perforation appears to have been 
enlarged, so that this platform with its parapet looks like a large mamelon. The 
boss slopes steeply with a convex curve, which suddenly becomes concave and 
ends in the rounded edge of an obsolescent basal terrace. Outside this there is 
neither a distinct scrobicule, nor any ornament other than the slight ridges already 
