42 
CRETACEOUS ECITINOTJERMATA 
amlnilacral plate, the last three or four somewhat obliquely descending towards the 
poriferous zone. Towards above and below the number of tubercles of course 
decreases. The mammelon is rather depressed, smooth, perforated ; the boss ring- 
like and scarcely elevated above the outer edge of the otherwise distinctly marked, 
roundly polygonal areola, the edges of Avhich when Avell preserved form rather sharply 
erenulated, almost straight lines between the tubercles, while the interspaces 
between the horizontal rows of tubercles are broader and uniformly very finely 
granular. 
The only specimen which distinctly exhibits the characters of the genus is, as 
already stated, not so far preserved as to render a perfect characteristic of the species 
possible, hut it can he readily distinguished from AT. Cotteani by the much smaller 
aperture, much greater number of tubercles on the intcrambulacra, and the finely 
granular siuTace between them. 
LocoliUj. — North of Poodoopolliam, in a white, impure limestone, together with 
Terehvalida sithdepressa. The small specimen above referred to is from a light 
brown calcareous sandstone south-east of Kullay. 
Formation. — Arrialoor group. 
Family —DIADEM A TIDFE. 
Cotteau, Pal. Fran 5 . terr. cret., vol. vii, p. 368. 
Wright, JIEMICIDAEIDM and mABEMAEM (ex parte). 
The test is in this family hemispherical or depi’cssed, and rounded or suhpenta- 
gonal ; the ambulacra arc wide, and the poriferous zones narrow, straight, or undu- 
lating, and generally with the pores in simple pairs, placed regularly under each 
other ; more rarely do the series of pores increase on the upper side of the test, hut 
thev never show that great ii’regularity in position which is commonly observable in 
the Eciiisiiue. The primary tubercles on both the ambulacral and interambulacral 
areas are hi- or mnlti- serial, on the latter sometimes of unequal size, and often slightly 
larger than on the ambulacra ; they arc either perforated or imperforated, and cre- 
nulated or smooth. Secondary tubercles arc, as a rule, well developed. The apical disc 
is small or of moderate size, composed of five genital and five ocular plates ; the 
upper right genital plate has madreporiform structure, and is usually somewhat larger 
than the others. The anus is central ; the mouth divided by ten incisions at the mar- 
gin, a character by which the members of the present family are readily distinguished 
from the Cibarid/e. The buccal membrane is covered with small unequal plates, 
irregularly disposed ; the dental apparatus composed of strong teeth. 
The spines arc elongate, aciculatc, cylindrical, or more rarely somewhat clavate, 
almost smooth or longitudinally striated, or Avith rows of granules, hut they never 
are spinous. 
( 112 ) 
