64 Triassic Echinoderms of Bakony. 
these he distinguished two kinds, namely the «tubercules miliaires» strewn over the extra- 
scrobicular surface, without perforation, mamelon, crenellae, or scrobicule, and the «tuber- 
cules papillaires» which always have a mamelon borne on a boss. He also recognised in certain 
species «tubercules granuliformes» (1835, p. 39) and «tubercules verruciformes » (1 835, pp. 42, 45, 
47, 50, 53), both of which he regarded as modified papillaries. D&SMOULINS may have adopted 
the term «miliaire»>, which means like millet seed, from the «Cidaris miliaris ... cujus 
Eminentiae Mili granulis aequales aut ‘minores» of KiEmn (1734), or from the «miliary 
eruption» of certain fevers, but not from the «miliary tubercle» of tuberculosis, It would 
be well to return to the usage of Desmoutins, to speak of all eminences that bear skeletal 
appendages as tubercles, distinguishing as papillaries those with a mamelon, and as miliaries 
those without one. The term papillaries has, however, dropped so entirely out of use, being 
superseded by tubercles (sensu restr.), that it cannot now be revived. The following scheme 
seems therefore the simplest and most practical: 
Minor eminences of the test are 
A) Appendage-bearing 
1. With distinct mamelon — Tubercles, 
further divided into primary, secondary, &c. according to their relative size in 
each species, 
2. Without mamelon — Miliaries, 
which may be close-set or sparsely scattered, regular or irregular, 
B) Bearing no appendages — Granules, 
which may vary in size, shape, and distribution, and are frequently to be 
regarded as products of the «Epistroma» (LOVEN). 
The sutures between plates or areas, or the margins of the plates, are said to be 
vertical when at right angles to the tangential plane which they touch; if at an angle 
to this plane they are said to be bevelled; if the angle formed by the sutural surface 
and the outer surface of the plate is less than a right angle, then the bevel faces inward 
and the margin is described as bevelled on its inner surface; if the said angle is greater 
than a right angle, the bevel faces outward. A succession of bevels in a meridional or 
transverse series produces imbrication. In a meridional series, if the adapical margins 
are bevelled on their inner surfaces, so that each plate overlaps its adapical neighbour, then 
the imbrication is adapical, and this is stated by Duncan to be the general rule for 
interambulacra,* If the adoral margins are bevelled on their inner surfaces, then the imbric- 
ation is adoral, and this is stated by Duncan to be the general rule for ambulacra.™* In 
the corona of Echinoids with two columns of interambulacrals, the only imbrication in a 
transverse direction is that along the adradial suture; and this, if it occurs, is generally, if 
not always, such that the interambulacrum overlaps the ambulacrum. In Echinoids with more 
than two columns of interambulacrals, such observations as have been made show a tendency 
for the admedian plates to overlap the outer plates. Consequently the general rule may be 
provisionally stated that transverse imbrication in Echinoid interambulacrals is adradial. 
In such thick-plated forms as Melonites, Oligoporus, and Palaechinus, the bevel of the 
adradial margin of the interambulacrum faces outward; but the bevel is so slight that JAcK- 
son & JAaGGaR (1896, Bull, Geol. Soc. Amer., VII, p. 154) are scarcely justified in calling 
* Exceptions are Pholidocidaris and Lepidocentrus ; see R. T. Jackson, 1896, Bull. Geol. Soc. 
Amer., VII, pp. 211, 244. 
** Astropyga, at least, is an exception, fide A. AGAssIz, 1881, Challenger Rep. Echinoidea, p. 71 
