76 Triassic Echinoderms of Bakony. 
a series according to the height and number of the interambulacrals, thus: 
T. persimilis, T. subsimilis, T. Liagora, T. Suessi, and T. subnobilis. Such an 
order also shows an increase in the definiteness of the scrobicular ring from 
T. persimilis to T. Liagora, but this progress is then interfered with by the 
increasing confluence of the scrobicules. Whether such an arrangement represents 
an evolutionary series is another question, on which some light is thrown by the 
species next to be described — T. praeternobilis. 
Triadocidaris > sp. indet. 2. 
Material. — A primary interambulacral tubercle, with all the extra-scrobicular 
and much of the intra-scrobicular portion of the plate missing; from Bed e 4 at 
Cutting VI on the Veszprém—Jutas Railroad; of Cassian age. 
Description of the Specimen. — Mamelon relatively rather large, perfo- 
rate, depressed hemispherical, very slightly undercut, diameter 1.7 mm., on a platform 
of 2.3 mm. diameter, with slight parapet, not much raised above scrobicule floor; diameter 
of scrobicule, circa 5.0 mm.; a scrobicular ring probably present, but only about two 
small tubercles remain at one corner of the specimen. Thickness of plate at scrob- 
cule, 0.7 mm.; to top of platform, 1.8 mm.; to top of mamelon, 2.25 mm. 
Triadocidaris practernobilis' n. sp. 
(Plate VI. figs. 185—138.) 
Diagnosis. — A Triadocidaris in which the ambital interambulacrals have 
scrobicules sunk, elliptical, confluent, and with no scrobicular ring. Extra-scrobicular 
interradial tract with secondary and tertiary tubercles alternating in meridional 
sequence, one of each on each plate; these are clearly mamelonate, perforate, 
scrobiculate, and are surrounded by quaternaries and miliaries dense and irregular. 
About 7 ambulacrals to each ambital interambulacral. 
Material. — a (fig 138) Fragment of an interambulacrum, comprising 
the interradial tract with two main tubercles on one side, their scrobicules incom- 
plete, and the margins of three scrobicules on the other side; from Jeruzsalemhegy. 
This is the holotype. 3 (figs. 135— 137) Fragment of an interambulacrum, consisting 
of two plates from which the interradial tract has been broken away; Railroad 
Veszprem—Jutas, Cutting I. Both are of Raiblian age. 
These two specimens supplement one another; indeed the only parts they 
have in common are the actual tubercles; but I have scarcely any doubt as to 
their specific identity. In the following description the portions referring to the 
adradial border are based on specimen Jb alone. 
Description of the Specimens. — The plates appear to be not far 
removed from the ambitus, and may therefore be regarded as fairly representative. 
The plates are low, with scrobicules sharply sunk, vertically compressed, and 
confluent, but sometimes limited by a slight ridge. The main tubercles are prominent 
and of peculiar shape: the mamelon, circular, flattened, very slightly undercut, with 
large perforation vertically elongate, rests on a fairly wide platform with slight para- 
pet; from the edge of this the boss slopes steeply downwards in a convex curve 
' Exreeding noble, to express the relation to T. subnobilis. 
