98 Triassic Echinoderms of Bakony. 
interambulacrals before us is Triadocidaris. In all known species of that genus, 
however, the scrobicules are definite and there are distinct secondary tubercles ; 
some have also tertiary tubercles, and all, except 7. subuobilis and T. praeternobilis, 
have a scrobicular ring. The very different character of the present plates, even 
though disagreeing with Duncan’s diagnosis of the Family Cidaridae (1889, p. 26), 
might be regarded as merely specific and a natural consequence of the enlarged 
radioles. That, however, would be admitting a modification of considerable extent, 
for even Goniocidaris clypeata, which DorpErLew introduced to science as «Eine 
recente Cidaris Buchi», has the scrobicular and other tubercles, with their radioles, 
perfectly well developed. More important than the suppression of tubercles is the 
nature of the various sutural margins. The adradial suture was indeed bevelled on 
its inner surface, and perhaps overlapped the ambulacra as in Triadocidaris, but 
it lacked the denticles so characteristic of that genus. The other sutures were more 
bevelled, and consequently more imbricate and flexible, than in any species of Triad- 
ocidaris. Hitherto it has not been suggested that the transverse sutures in that 
genus were anything but vertical We have, indeed, seen that there was some 
bevelling and grooving in the Bakony species; but this was not enough to 
cause the plates to fall asunder on the death and decay of the animal. As for 
the interradial suture, the bevelling of it which is here seen is not met with 
in Triadocidaris. 
All these differences seem to warrant the separation of Avaulocidaris from 
Triadocidaris and the other Cidaridae, and its maintenance as an independent genus. 
Whether the loose union of the interambulacrals exemplifies the retention of 
an ancestral character or an apparent reversion to it consequent on the evolution 
of the «testudo», cannot be decided. Another point of similarity to a possible 
Palaeozoic ancestor lies in the peculiar nature of the miliaries, for they seem less 
like ordinary tubercles than the ends of faint ridges radiating from the boss. Just 
such ridges, merging into tubercles, are characteristic of Echinocrinus AG. restr. 
Lampert (synn. Archaeocidaris M’Coy, Palaeocidaris Drsor). The occasional ele- 
vation of the scrobicule as a sort of basal terrace is also reminiscent of that genus. 
These two structures are admirably shown in plate XXII, ff. 2 and 6 of TornguisT 
(1897, Abhdl. geol. Specialkarte Elsass-Lothringen, V., Heft VI). 
Plegiocidaris, 
1883. Plegiocidaris A. PomeL, «Classif. méthodique et genera des Echinides», Thése Fac. Sci. Paris, 
Alger, p. 109. (Reprint, Paléont. Algérie, Echinodermes, Livr. 1. 1887). 
1900, Plegiocidaris PomrL, J. LAMBERT, Bull. Soc. Sci. Yonne, LIII (1), p. 40. 
1902. Plegiocidaris Pome, J. Lampert, «Ech. foss. Barcelone>, Mem. Soc. geol. France, Pal., IX, 
fase. (sp oO: 
1903. Plegiocidaris POMEL, em. L. Savin, «Ech. foss. Savoie», Bull. Soc. Hist. Nat. Savoie (2) VIII 
p. 207. (Author's copy, p. 153). 
1904, Plegiocidaris Pomel, DELaGE & HéRouarp, «Traite de Zool. Concrete,» III, p. 228. 
Diagnosis. — A Cidarid of variable size and normal shape, with plates united 
by rigid suture. Ambulacra flexuous, unigeminal, with a double row of imperforate 
tubercles, and perradial tract bordered by equal regular miliaries. Interambulacral 
tubercles few, scrobiculate, crenelate, perforate. Radioles inverticillate, elongate or 
glandiform, granular or spinose. 
When Pome (1883) founded the genus for «Cidariens» with «Tubercules 
ao 
