30 
directions, several intercurrent lines, on which minute granular 
tubercles are very thinly disposed; whilst the general surface is 
covered with tubercles of rather a larger size. The mouth is small, 
and nearly round, according to Leske : its situation is, however, not 
pointed out, nor am I able to point out its situation in either of the 
three specimens which I possess. The anus is round, and placed in 
the upper margin of the narrower, and apparently truncated termi- 
nation of the shell. 
From some peculiarity of structure of this shell, the specimens are 
almost always distorted. Such is the case with all the specimens 
which I have seen, and with most of the representations of them. 
The recent shell is figured with its spines, in the sixth volume of 
Encyclopedic Franqois, PI. lix. Fig. 4. The fossil is mentioned and 
figured by many authors, but none of the figures appear to exceed 
those of Scilla. The specimen figured in the present work, Plate III. 
Fig. 12, is from Malta. 
Spatangus pusillus, Tab. xxiv. c. d. e. Klein, et Tab. xxxvm. 
Fig. 5, chiefly distinguished by a deep dorsal groove, has not, I con- 
jecture, been yet discovered fossil. 
Spatangus radiatus. This species is only found in a fossil state. 
The shell is of an ovate circumference, and of a vaulted galeated 
form. The vertex is pierced with four foramina, where four trans- 
versely striated and biporous ambulacra arise. Two of these pass 
nearly half way down the shell, obliquely directed on each side of the 
posterior part : a dorsal lacuna also, in which are two double rows of 
pores, originates from the vertex, and, passing down the anterior 
part of the shell, is extended to the mouth. The shell is formed 
chiefly of pentagonal assulae. The mouth, which is situated in an 
oblong pit, in the broader and anterior part of the base, is reniform, 
and beset with pores and tubercula, disposed in somewhat of a stel- 
lular form. The anus, which is nearly round, is placed in a pit at 
the posterior part, close above the margin. The shell is remarkably 
