32 
verse risings are observable over the whole upper surface. The flat 
raised surface, on the posterior part, is raised much above the rest. 
On this surface, ten sets of tubercles, lessening as they approach the 
margin of the area, are obliquely disposed, in two rows. On the two 
lateral raised surfaces, a like number of sets of tubercles are disposed, 
so as nearly to form angles along the central line. The rest of the 
surface appears to have been beset with numerous small tubercles ; 
the larger of which, being connected at rather acute angles, with the 
tubercles of the raised surfaces, form undulating lines, giving, in 
many places, the figure of the letter W. From the ridges above 
mentioned proceed the angles observable in the circumference of the 
fossil ; and from the transverse risings, the surface of the shell is 
formed, as it were, into numerous facets. This description of the 
recent echinus will be found to apply very nearly to the fossil here 
represented : the difference being only that which proceeds from the 
injurious changes which the fossil has sustained. 
The inferior surface of the fossil is nearly destroyed ; but from 
Leskc’s account, we learn, that it very nearly resembles that of Spat, 
pusillus, and Spat, striato-radiatus. The mouth is oval and trans- 
verse ; the upper lip not covering, nor much projecting over, the 
under lip. In the superior margin of the narrow end is the trans- 
verse oval anus ; and, in the inferior margin, is a reniform area. 
Similar specimens are, I believe, rare. It has, however, been 
figured by Aldrovandus, Mus. Met. p. 4/5 ; Scilla, Tab. xi. Fig. 1 ; 
and by Allion, the editor of the French edition of Klein, and of the 
French Encyclopedia. 
Spatangus depressus, Tab. li. Fig. 1, 2, Lesk. Under this species 
are included those echinites which are of a flattened upper surface, 
of a subrotund and cordated figure, proceeding from a dorsal groove, 
and having five pair of ambulacral biporous rows : one pair, in some 
varieties, passing along the dorsal groove. The mouth is transversely 
placed in the centre of the base, and the anus in the middle part of 
