Echinoid Tests, Diademoida. : 115 
second or every third ambulacral. The presence of these tubercles is flatly opposed 
to the generic diagnoses of Neumayr and Lampert. The jaws and radioles also are 
described and figured by QueEnsTEDT. 
(4) ? Leptocidaris blaburensis QuENstTeDT (1875, pl. 69, fig. 71), Kimmeridgian. 
There is a mistake here, since fig. 71 is Leptocidaris triceps, and this cannot be 
the species intended because the ambulacrals are distinctly majors of 3 elements. 
Fig. 72 is named Cidaris blaburensis in the explanation of the plate, but Lepto- . 
cidaris in the text (p. 233). This appears to show distinct primary ambulacrals, but 
since the fossil is an internal cast the evidence is not satisfactory, and in any case 
the appearance is as much like Cidaris as Mesodiadema. 
(5) Mesodiadema simplex Lampert (1900, p. 31), Middle Lias. Test rotular ; 
diam., 12 mm.; height, 6 mm.; peristome wide; main tubercles 7—8 in column, 
slightly developed, on adradiaf border, perforate, noncrenelate, with scrobicules well 
developed, circular, and contiguous; interradial tract wide. 
(6) Cidaris Admeto Quenstepr (1875, pl. 68, f. 143 non 144) non Ménsr., 
Carnian, might equally well be Hemipedina. The figure is inadequate. 
(7) Mesodiadema Lamberti Atracut (1905, p. 4, pl. I, f. 3, 3a), Middle Lias 
of Rocchetta near Arcevia. Diam. of test 17 mm., height 8 mm.; diam. of peristome 
3.5 mm. Interambulacra very broad; main tubercles, 6 or 7 in column, perforate, 
scrobiculate, more developed in the adapical half of the corona than in the adoral, 
where they atrophy and are confused with the general ornament; scrobicules cir- 
cular, distinct ; extra-scrobicular ornament of fine and close-set miliaries. The figures 
are not clear, and it is not stated which represents the adoral surface, but I take 
it to be fig. 3. The figures represent the extra-scrobicular miliaries as relatively 
coarse, and the scrobicules as small and well-marked. The reference of this species 
to Mesodiadema is approved by Lampert. 
Arranged in order of age the undoubted species of Mesodiadema are therefore: 
M. Marconissae (Desor). . . Toarcian . . . Italy 
M. Lamberti ArracHt. . . . Pliensbachian . . » 
M. simplex LamBertT . . . . Pliensbachian . . France. 
Thus, although Mesodiadema is, on morphological grounds, regarded by 
Lampert as the ancestral form of all genera with perforate non-crenelate tubercles 
(Pedininae), still it has not hitherto been known with certainty below the Middle 
Lias. It is therefore interesting to find in the Bakony material specimens which, 
though fragmentary, seem to have a good claim to be placed in this genus. The 
fragments capable of reference are confined to interambulacrals. The straight and 
regularly denticulate adradial margins of these fragments indicate that the ambula- 
crals, and consequently their pore-pairs, were in simple series, but do not warrant 
the predication that the ambulacrals were non-tuberculate. The interambulacrals, 
however, agree so closely with those of the recognised species of Mesodiadema, 
not merely in the generic character of perforate, non-crenelate tubercles, but in 
the position of those tubercles near the adradial margins, the restriction of other 
ornament to fine close-set miliaries, the considerable relative width of the plates, 
their combination in one species into an almost flat area denoting a depressed 
rotular test, and finally the absence in that species of any definite gill-notches on 
the peristomial border, that it would not be reasonable to refer them to any other 
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