Echinoid Tests, Cidaroida. 69 
Diagnosis. — A Cidarid with the adradial margin of the interambulacrum 
obliquely bevelled on the inner surface and denticulate, thus flexibly imbricating over 
the ambulacrum. Main interambulacral tubercles perforate, non-crenelate, with large 
scrobicules, either distinct or confluent. Podial pores not yoked. 
This differs from Prof. DorperLEIN’s diagnosis mainly in the omission of the 
statement that the scrobicules are not sunk; they may be either flush or sunk. 
DorpERLEN referred to his genus four species in the following order: Cidaris venusla 
Monst., C. subsimilis Moyst., and C. Liagora Mbwsv., all with distinct scrobicules, 
and C. Suessi Lause with confluent scrobicules. He did not however fix on any 
one of these as genotype, and since Lampert (1900) has removed C. venusta to 
Microcidaris on account of its vertical and rigid adradial sutures, it is advisable 
definitely to adopt as genolectotype the next species, C. subsimilis. Lampert (1900) 
has added to the genus Cidaris subnobilis Minsr., which DorperLem (1857, p. 40) 
had doubtfully referred to Miocidaris. None of these species is found in Bakony, 
but there are the remains of Triadocidaris persimilis n. sp. and of one or two 
indeterminable species from the Cserhat group, and of T. practernobilis n. sp. from 
the Jeruzsalemhegy group. The names given are intended to imply that the two 
species emphasise, the features of the St. Cassian 7. subsimilis and T. subnobilis 
respectively. The Jeruzsalemhegy group also furnishes a species, 7. tmmunita, which 
shows resemblances to both Anaulocidaris and Mesodiadema. 
The most interesting character in Triadocidaris, as in some other early 
genera, is the flexibility of the adradial suture. This feature, to which Prof. DoEDERLEIN 
first drew attention (N. Jahrb. Mineral. 1887, II, pp. 1—4, pl. i), has been held by 
Lampert (1900, p. 53) to warrant the separation of such Cidarid genera as a Sub- 
Family Streptocidarinae opposed to the remaining genera, which all have rigid 
adradial sutures and constitute the Sub-Family Stereocidarinae. LamBert’s Strepto- 
cidarinae would thus include the Triadocidaris and Miocidaris of DoEDERLEIN, and 
Eotiaris Lameert 1900. This last however it is difficult if not impossible to separate 
from Miocidaris, as will be explained later. Thus the Streptocidarinae’ come to 
consist of only two genera, which differ solely in the bosses of the main tubercles, 
those of Triadocidaris being plain and those of Miocidaris crenelate. Study of the 
Bakony Echinoids and re-examination of other Permian and Triassic species, while 
confirming the broad fact of flexibility in the adradial sutures of these genera and 
indeed extending it to species that appear to be primitive Ectobranchiata (e. g. 
Mesodiadema), nevertheless indicates that the transition from a flexible to a rigid 
union was — as one would have expected — extremely gradual, and that in a 
single individual the union might be flexible in one region of the adradial suture, 
but rigid in another region. Consequently, as Lampert’s transference of 7riadocidaris 
venusta to Microcidaris has already exemplified, this feature alone does not always 
enable one to distinguish even genera, and still less is it a suitable criterion for the 
distinction of two Sub-families. At most one can speak only of a Streptocidarine 
Grade or stage of evolution. But even this is in some respects misleading, since 
such a stage is by no means confined to Cidaridae. The flexibility of the adradial 
suture is but part of a general flexibility common to many of the older Echinoidea 
and manifested also in the sutures between the interambulacrals themselves. Tria- 
docidaris and other Triassic Echinoids are passing from this Streptosomatous stage 
to the Stereosomatous condition found in the majority of later forms. The nature 
