APPENDIX I. 
SUMMARY* OE THE EEITISH LIASSIG AND OOLITIC 
ECHINOIDEA, ASTEEOIDEA, AND OPHIUEOIDEA, 
Described in Volumes I and IT of the Oolitic EcJiinodermata. 
Order I.— ECHINOIDEA, Wri^/a (Vol. I, pp. 4, G— 16). 
Body-shell (test) spheroidal, oval, cordate, or depressed^ without arms, furnished with 
a distinct mouth {o?'al ajjeni??^), whose border (peristome) is sometimes simple, some- 
times lobed, always on the under side, and generally armed with five calcareous sets of 
plates (jaics). Anal opening variously situated on the upper or under side, or on the 
marginal border. Body enclosed in a shell (test), composed usually of twenty, sometimes 
of more than twenty (as in the family of the Palaeozoic Ferischoechinida), columns of 
calcareous plates, forming, in either case, ten areas. Five of the areas (amhidacral) 
containing each two rows of apertures (poriferous zones) for the passage (in the living 
state) of retractile suckers (amhidacral tubes). The other five areas (inter amhidacral) 
destitute of sucker-pores. Ambulacral pores disposed in single pairs (unicjeminal), 
double (hifjeminal), or triple oblique (trigeminal). Ambulacral pore-columns (areas) 
sometimes continuous from the peristome to the summit (complete), sometimes confined 
to the upper surface of the test (interrupted), or forming re-entering curves (petaloid). 
Surface of test studded with tubercles (primary, secondary, and miliary), possessing 
spines of various forms and dimensions. Spines articulated on the rounded upper part 
of a tubercle (mamelon), which rises from a conical process (boss). Base of tubercle 
surrounded by a round, oval, smooth, excavated space (areola or scrobicide). Summit of 
test marked by an apical disc, composed generally of five genital and five ocular plates, 
usually in contact and central. Cutaneous surface of shell, especially .near the mouth, 
bearing small tripartite, pincer-like bodies (pedicellaria), placed on a short stalk, whose 
lower portion encloses a calcareous nucleus. Pedicellariae capable (in living state) of 
seizing small bodies and passing them from one to the other. Movement of the animal 
effected by the motion of the spines and the ambulacral tubes. 
The EcHiNoiDEA (including the Perischoechinidse) range from the Silurian to the 
* Compiled by the Eev. T. Wiltshire, M.A., F.G.S., Hon. Sec. Pal. Soc. 
^ 23 
