Echinoid Tests, Cidaroida. 87 
on the outer limit of the bevel which stops the plate next above it from sliding 
right over it. Similarly, of the interradial margins the adoral one is «nach innen 
abgeschragt» and the adapical one «nach aussen». The correctness of this account 
depends on the meaning to be attached to «nach innen» and «nach aussen». Now 
SPANDEL goes on to say that the adradial margin of each interambulacral is «nach 
innen abgeschragt», and it is admitted by all that this faces inwards. Therefore it 
would seem that, according to SpanpEL, the adoral transverse margin has a bevel 
facing inwards; but this is incorrect. On the other hand Spanpet's figures (pl. XIII, 
f. 4 a & b) are clearly meant to show that the convex adoral margin has a bevel 
facing outwards; and this is correct. We might therefore translate «nach innen 
abgeschragt» as «with a bevel facing outwards», and suppose that in describing 
the adradial margin Spanpet had written «<innen» for «aussen» by a lapsus calami. 
Unfortunately the question is further complicated by the statement that «an der 
ausseren Grenze der Abschragung des oberen Randes liegt eine Leiste, u. s. w.»; 
for in his section across an interambulacral (pl. XIII, f. 2) SpanpEL has drawn this 
ridge on the outer limit of the bevel facing outwards, which we have just decided 
must be the adoral («untere») margin. 
The actual facts, as ascertained from an independent examination of specimens 
of Miocidaris Keyserlingi (Brit. Mus., E1119, E1121), may be thus expressed : 
orad- 
interradial 
apicad- 
interradial 
Marcin — adradial | adapical | adoral 
BEVEL FACING — inwards inwards | outwards inwards outwards 
ridge ridge 
NATURE OF transverse | on inner | on outer 
: ‘ ; smooth smooth 
SUTURE denticles | margin, margin, 
sometimes] usually. 
Essentially the same structure obtains in MW. Cassiani, as observed in the 
lectotype and in Brit. Mus. E8552. It may also be seen in Miocidaris sp. (Brit. 
Mus. E8553) from St. Cassian; in a plate of Miocidaris sp. from the Cassian beds 
of Cserhat; in Miocidaris planus from the Raiblian of Jeruzsdlemhegy; and in a 
plate of Miocidaris sp. from the same horizon at Cutting I on the Veszprém-Jutas 
Railroad. Quenstept (1875) does not mention it in M. amalthei or M. arietis, but 
if the plates are so cleanly isolated as his figures (pl. LXVII, ff. 3, 5, 6, 21, 55) 
imply, then the suture must have been a loose one. I have not observed the 
bevelling in M/. verrucosus, but the material scarcely warrants an assertion of its 
absence. In M. subcoronata, however, the large plates have almost or quite vertical 
sutures, with only a faint trace of a median depression; and this perhaps shows 
that DoEDERLEIN was right in separating this species from Miocidaris. 
The supposition that in all these species the bevel facing outwards is adoral 
rests partly on my own observations, partly on accepted statements as to the 
imbrication in Echinoidea generally, and especially on the conclusions of A. Torn- 
guist in his excellent «Beitrag zur Kenntniss von Archacocidaris», in which genus 
the meridional imbrication of the interambulacrals is adapical. Just as the denticulate, 
overlapping, adradial suture of Triassic Cidaridae is only a stage in phylogenetic 
