PLATE 2L 
ENTROCHIT^. LIMESTONE AND SPAR. 
FIG. 1, 2, 
The common Entrochites — (See plate 2, fig. 1, 2, &c.) 
Fig. 1. We have observed in a preceding part of this 
work, that the fossil Entrochi vary considerably in shape. 
The specimen now figured, differs so much in external 
appearance from that which is given in Plate 2, fig. 1, that 
a casual observer would scarcely consider them as the same 
species. They are both, however, even, cylindrical, and 
jointed ; perforated through the centre, and furnished with 
lateral arms or branches. The principal difference consists 
in the joints being smaller, and the branches (in proportion 
to the size of the stem) considerably thicker in the present 
fossil, than in that before delineated. But we conclude the 
recent animals not to have been distinct, as the petrifaction 
is found in every intermediate size and form between the 
two varieties here noticed. 
a. a. a. Cavities from which lateral branches proceeded. 
b. b. b. Fragments of the branches remaining in the stem. 
2. The first joint of one of the branches, or that part 
which is immediately inserted into the stem — On one side 
convex, correspondent to the cavities a. a. a. fig. 1 — marked 
