122 Triassic Echinoderms of Bakony. 
The mode of union between the plates, combined with their large number (as 
estimated above), must have produced a test of considerable flexibility. 
The following are measurements in millimetres: 
a b c d e F g h m n 0 Pp 
Widthit*-. feo 7.44 7.7 744+ 7.8 6.4 6.4 5.4 rid 7.4 tit ABS 
Heights anes ees eee 1.3 1.8 2.7 1.4 2.6 1.4 1.4 Del. 2.0 1.5 a4 
Diameter of scrobicule 
(transverse) . . . 2.7 incomplete 3.2 2:55? 1.9 24 16 18 26 2:8 26° 2:9 
Diameter of boss . . 1.3 1.0 1.3 1.5 0.8 1.3 0.8 1.0 1.4 1.4 1.1 1.3 
Diameter of mamelon. 0.75 0.5 0.5 0.8 0.4 0.5 0.35 04 0.7 05 O4 0.6 
Distance of tubercle 
from adradial margin 3.6 ? 3.9 3.7 2.5 3.6 "2:5 2.9 4.5 4.3 3.1 3.5 
Thickness of plate . 045 0.35 (02° 05 05 05 045 04 05 05 05 06 
No. of adambulacral 
notches erie. coos 3 4? 4 ? 4 3 3 3 a 4 
Description of Specimen w (Fig. 202). — This is from beds a—b of 
Cutting IV on the Veszprém-Jutas Railway, of Cassian age. It appears to be part 
of a plate from the b column, and to consist of the greater part of the interradial 
tract with a little bit of the scrobicule. The height of the plate is 4.1 mm. The 
extra-scrobicular ornament consists of small tubercles, irregularly distributed, about 
1 mm. apart, with a few minute, but apparently still mamelonate, tubercles here 
and there between them. The scrobicule is flush. The adapical margin has a slight 
concave curve, and the adoral margin a corresponding convex curve. The edges 
are grooved. The plate is 1.2 mm. thick. 
Except for its greater size in every way, this fragment. closely resembles 
M. lata, and is conveniently described here. If the whole plate were known, it 
would probably be found to belong to some quite different genus, possibly Miocidaris. 
Description of Specimen ~. (Fig. 211). — This is from the Cassian beds 
of Cserhat. It consists of the tubercle with its scrobicule and a small part of the 
extra-scrobicular surface. The scrobicule is slightly sunk. The extra-scrobicular orna- 
ment consists of close-set irregular miliaries, about 3 to the millimetre (linear). 
Height of plate 2.3 mm. Diameter of boss, circa 1.3 mm. Diameter of mamelon, 
0.6 mm. Adoral and adapical margins bevelled and grooved. Thickness of plate, 
0.5 mm. 
No difference can be detected between this fragment and one of the larger 
plates of M. lata. If it really is that species, the locality must be considered 
doubtful. 
Relations of the Species. — The absence of any secondary series of 
tubercles removes this species from Diademopsis; and the relatively small size of 
the main tubercles, coupled with the absence of all tubercles from the extra- 
scrobicular ornament, removes it from Hemipedina (s str.). On the other hand the 
tuberculation and ornament agree with that of some species referred to Mesodiadema, 
e. g. M. Marconissae and M. Lamberti. The reference to Mesodiadema therefore 
seems justified. 
From the known species of Mesodiadema, M. lata differs in the greater relative 
width and probably in the greater number of its interambulacrals. 
It is interesting to compare the mode of union between the plates with Duncan’s 
careful description of the structure of the sutural margin in Diadema setoswm and 
eet 
