CidakidjE. KADIATA. Asteroiuea. 393 
Family V.— ECHIN0LAMPASIDJ3. 
and this is coveted with a series of vibratile cilia. 
Tliese organs, as Mr. Gosse observes, are so unique 
in their forms and functions, so apparently inde- 
pendent of the animal’s will in their movements, 
that it was long a matter of dispute whether they 
were truly organic appendages or merely parasitic 
intruders. The family is well represented in Plate 2, 
figs. 1, 2, 3, 4 — fig. 2, Echinus miliaris ; fig. 3, Echinus 
elegaus ; fig. 4, Echinus sardicus ; and fig. 1, Echino- 
metra mammillutus. 
Family II. — CIDARID^ {The Diadems). 
This family is distinguished from the Echinidse by 
having the tubercles to which the spines are affixed 
pierced with a central pit. Through this perforation 
a small muscle passes, which is attached to the spine, 
and by means of w’hich it is moved. The shelly case 
is globose, the ambulacra continuous from mouth to 
anus, and the spines are of several forms. The family 
is divided into a considerable number of genera, and 
contains many species. It is represented in Plate 1, 
fig. 2, by Diadema Jistularis^ exhibiting the spines 
with which the case is covered; fig. 1, Aslropyga 
radiata, with the spines removed to show the structure 
of the shell ; and fig. 4, Ciduris imperialis. 
Family III.— SCUTELLIDAE {The Cahe-ur chins). 
The Cake-urchins have a thick, pentagonal shell 
composed of twenty bands of pieces, like the Echinidae. 
It is elliptical or circular, and covered with small, uni- 
form bristles. This crustaceous covering is usuall}' 
thickened internally by an additional coat, and is 
strengthened by internal columns, which enable these 
brittle-looking shells to resist the action of the sea for 
a length of time. The ambulacra are formed of single 
series of double bores, forming petal-like impressions 
on the dorsal surface ; while on the under surface there 
are peculiar ray-like furrows going out from the centre 
and ramifying all over il. The vent is posteiior, and 
placed near die margin. The mouth is five-sided, and 
the jaws are composed of five horizontal plates. This 
family is represented in Plate 3, fig. 1, by Echinan- 
thus (Clypeaster) subdepressus ; fig. 2, Arachnoides 
placenta ; figs. 3, 4, liutula Augusti. 
Family IV.— GALERITID^. 
The shelly case in this family is thin, elongate or 
sub-circular, or sub-conic, and is covered with very 
fine bristle-like spines set on very close, small tuber- 
cles. The mouth is central and destitute of jaws. 
The vent is inferior and placed on the posterior mar- 
gin. The ambulacra are arranged in a single series of 
double pores. The body, like the Echinidae, &c.', is 
formed of twenty vertical bands, the ambulacral bands 
being the narrowest. The family is represented on 
Plate 4, figs. 1, 2, by Galerites albo-galerus., a fossil 
species ; and figs. 3, 4, by Echinoneus minor. 
VoL. IT 106 
The shell in this family is elongate or sub-circular 
and covered with very small, uniform bristles, which 
are set upon small tubercles that are scattered 01 
placed in series. The mouth is central, or rather in 
front^of the centre, and is destitute of jaws. The vent 
is posterior, dorsal, or inferior ; and the ambulacra are 
formed of two series of double pores. The family is 
represented in Plate 3, figs. 7, 8, by Cassidulus Caribat- 
arum ; Plate 4, fig. 5, by the fossil species Echinolam- 
pas Konigii; and fig. 6, Echinobrissus Breynii, also 
fossil. 
Family VI. — SPATANGID.® {The Heart-urchins). 
The shelly covering in this family is thin, elongate 
or sub-circular, with an anterior dorsal groove, gene- 
rally heart-shaped, and like the other Echinoidea, 
formed of twenty bands of pieces. It is composed of 
large polygonal plates, few in number, and is covered 
with crowded, uniform, hair-like spines, with larger, 
longer ones placed on perforated tubereles, and band- 
like fascicles covered with very short, minute spines. 
The vent is terminal, and rather above than below the 
terminal border. The ambulacra are short, petal- 
shaped, and are only four in. number. This family is 
represented in Plate 4, figs. 12, 13, by Brissus ventri- 
cosus ; and figs. 9, 10, by Schizaster Atropos. 
Order II. — ASTEROIDEA {Star- fishes). 
The Star-fishes, or Sea-stars as they are often 
called, differ considerably from the previous order in 
many respects. Instead of having the soft parts of 
the body covered by a hard, calcareous case, the Star- 
fishes have them protected by a coriaceous, leathery, 
or cartilaginous skin, strengthened by calcareous plates 
imbedded in its substance, and in which are implanted 
spines or tubercles. The body is expanded into a 
series of arms, generally five in number, frequently 
more, varying from eight to thirty, and of the same 
structure as itself. The under surface of these arms 
is marked with gutters or grooves proceeding from 
the mouth in the centre of the disc to the very tip, 
and which are called the ambulacra or avenues — 
answering to the same parts described by that name in 
the Echini. These gutters are pierced, as in these ani- 
mals, with several rows of small holes, through whieh 
issue tentacula with expanded tips capable of contract- 
ing and elongating themselves. It is by means of these 
tentacles, acting as suckers, that the animals are enabled 
to walk. The mouth of the Star-fishes is always placed 
in the inferior centre of the rays. This leads to the 
stomach, which is in form of a bag, and which pos- 
sesses only one aperture, through which the food is 
received and the indigestible part rejected. From this 
stomach two branched caeca extend to each ray. The 
food of these animals consists of young shells, small 
Crustacea, and other marine creatures. They have the 
