( m ) 
ANOCYSTI. 
In those species in which the mouth and vent are at opposite ends 
of the axis of the animal, the body is globular or hemispherical, and di- 
vided into ten compartments by ten avenues of pores. The avenues 
approach in pairs, making five of the compartments smaller than the 
others with which they alternate. The smaller compartments consist 
of a double row of plates, united to each other by a zig-zag line, and 
to the larger compartments by a straight subserrated suture. Each 
plate is covered with tubercles, on the surface next its fellows, in the 
same compartment, but on the surface towards the opposite side, it is 
perforated with pores, in pairs, and arranged in oblique lines, with an 
oral direction. The portions of the plate, with the pores, are frequent- 
ly compound. These plates increase in size, from the mouth to the 
middle of the body, where the avenues of the pores are at the gi’eatest 
distance, and then decrease to the pelvis, where the pores approach, 
and terminate in a pentagonal costal plate. In the inside of the mouth 
there are five plates perpendicular to the margin, and perforated in the 
middle, from which the smaller compartments take their rise. The 
large compartments likewise consist of a double row of plates, united 
by a zig-zag line, covered with tubercles without pores, widest in the 
middle of the body, and terminating in the five plates of the pelvis, 
one of which, termed the 'wart, is curiously puckered, and all of them 
have a large perforation. These plates form the ring of a circular 
space, covered by a tough skin, with tubercles, and perforated in the 
centre by the vent. Around the mouth there is likewise a circular 
space, formed by a tough muricated skin. The whole body is covered 
with an integument, more or less intermixed with muscular fibres. 
The appendices of the skin are of three kinds. 1. The prickles are of 
different sizes, and are seated on the convex surface of the tubercles, 
which are received into their concave bases, thus forming a ball and 
socket joint, surrounded by the integument, and put in motion by its 
agency. These serve the purpose of defence, and assist locomotiou. 
Their structure is radiated from the centre, with distinct traces of con- 
centric layers of growth. Mr Haidinger, in his translation of Mohs's 
Mineralogy, vol. ii. p. 91, has stated, that, in a fossil state, “ every 
one of the spines of Echini consists of a single individual (Rhombohe- 
dral Lime Haloide) perfectly cleavable, and the axis of which is paral- 
lel to the axis of the spine. But, what is still more remarkable, the 
spines of these animals possess the same property, even in recent 
specimens of the latter, and it appears, that the carbonate of lime crys- 
