340 
POPULAR SCIENCE REVIEW. 
Ophiurans were in existence, and attention is directed to this 
fact, as it is with the class of Ophiurans that this communica- 
tion deals. 
There is no mistaking an Ophiuran, for its round flat body 
and its five slender plain or spiny arms, the whole as a rule 
being scaly and of many colours, distinguish it from all other 
things. They are of very different sizes when full grown ; in 
some the body is an inch and a half across, and in others not 
more than a few lines. In most, the contour of the body is 
circular and flat, but in some it is pentangular, and it may be 
tumid or even constricted between the arms. These last vary, 
wonderfully, in their size, shape, construction and ornamentation, 
and in some instances the number five, so peculiarly character- 
istic of the Echinodermal structures, is departed from, and six 
arms exist. Moreover, it is by no means certain that some kinds 
have not different numbers of arms, at different periods of their 
lives. The top and sides of the body, are either covered with a 
skin, or else with geometrical plates or scales united at their 
sides or overlapping ; they are often more or less covered with 
granules, little spinules, and even with groups of spines. 
Black, red, yellow, green, white, brown, and grey, either pure or 
in all sorts of tints, are common colours in the skin and spinules, 
and the plates are splashed with the same colours. The colour 
may be universal or in parts, especially in rings on the arms, 
and in some instances the reptile-like look of the body and arms 
is maintained by a square brown or white pattern greatly re- 
sembling that seen on many Ophidia. The plates are often 
arranged in beautiful patterns, a rosette being central with radii 
of plates in the space between where the arms fit in to the 
upper part of the body in a sort of notch. And as the plates 
vary in size as well as being in squares, hexagons, pentagons, 
and rectangles, every opportunity is given to Dame Nature’s 
love of organic aesthetics. Close to where the arms come in, on 
the top, there is usually, but not invariably, a notch for them, and 
between it and the centre are certain plates which are constant, 
but are sometimes hidden, being covered with skin. Two of 
them are found on either side of the track of the arms, and not 
far from the margin or edge of the body above. They are called 
Kadial shields, (fig. 1, a) and as one is on either side of the 
arm they are in pairs, there being five pairs in all, and six when 
there are six arms. On either side of the arm notch, or even 
nearer the centre of the upper surface, these ten plates give a 
character to the animal, when they are well developed. 
The sides of the body are between the arms, and are usually 
scaled or plated, being spinulate or not. In some they are naked, 
that is to say, covered with skin which has little carbonate of lime 
in it in the form of scales or plates. When the animal is placed 
