40 
Fig. 29, where you will have one instance of the strange, and even 
absurd errors, to which we are liable in these pursuits. A specimen, 
not indeed so well defined, is there given as part of the branch of a tree. 
To mistake the spine of an echinus for the branch of a tree, you may 
say, is pretty well ; but this is trifling — I will now confess to you, that 
in the same plate, we both narrowly escaped the misfortune of having 
part of the tusk of an elephant introduced as part of the stem of a tree. 
I mention these circumstances, to impress on your mind the great 
chance of error in these pursuits, from the obscurity of specimens and 
the similarity of appearances, in even most different bodies. But to 
return : — The fossil just mentioned, Plate IV. Fig. 5, is a very curious 
variety of this species, torosa, from Giengen, in Swabia, being the 
compressed serrated spine which is mentioned and figured by Andrea 
and Leske. At its inferior termination, part of its articulating head 
is yet to be seen. Thence it assumes a compressed triquetral form, 
beset both on its edges and faces with denticulated noduli. This is the 
Bacolo di santa Paulo of Scilla, Tab. xxiv. Fig. 2. Representations 
of fragments of knobbed spines are given in most writers on this subject. 
No fossil specimen of the genus Sudes fortalitiorum, pallisadoes, 
has, I believe, been yet known: I shall therefore be under the 
necessity of offering my observations on such fossils more at large, 
than the space, to which I find myself limited, has allowed me to 
treat of the former species. 
The genus Sudes fortalitiorum, pallisadoes, is divided by Klein into 
two species, the plain and the variegated with bands. For an instance 
of the former, he refers us to Rumphius, Tab. xm. d. d. d.; and, of the 
latter, he gives figures of twenty-two varieties, de Aculeis echinorum, 
Tab. xxxiv. Of the spines of this genus, he observes, the substance of 
which they are formed is very different from that of which the spines of 
all the other genera are composed. Whilst all those belonging to the 
class Acicula, and to the genus Sudes villarum , are formed of a substance 
whichhas a spathose appearance, those belonging to the Sudes fortaliti- 
t 
