MARSUPITES. 
115 
The fossil remains of this zoophyte have lii- 
therto been found only in the u})per chalk of 
Sussex, Wiltshire, and Yorkshire, and, like most 
other crustaceous bodies enclosed in this form- 
ation, are transmuted into a spathose calcareous 
S})ar. 
Hut one species is known ; the following de- 
scription will therefore illustrate both the generic 
and specific characters : — 
This fossil is generally of a suborbicular form, 
more or less distorted, with the lower extremity 
closed and obtuse, and tiie np})er, truncated and 
o})en, being tilled with chalk or flint. It is com- 
j)osed of numerous thin angular plates, that are not 
united as in the echinites, but are simply held in 
aj)position to each other, by the chalk in which 
they are imbedded. The name of “ cluster sto?ies,** 
given them by the Sussex quarry-men, not inaptly 
expresses their general appearance. 
The pelvis, or cavity in which the viscera of the 
animal were contained, is very capacious, and is 
composed of sixteen angular convex plates, arranged 
in the following manner, viz. 
1. A pentagonal plate (abdominal) placed in the 
centre of the base. 
2. Five pentagonal (costal) plates, attached to 
the sides of the centre. 
3. Five hexagonal (intercostal) plates, placed 
between the superior angles formed by the union 
of the costid. 
4. Five pentagonal (scapular) plates, filling up 
the angles in the superior margin of those last 
described, each having a semilunar depression on 
I 2 
