62 Dr. T. Wright on Fossil Echinoderms 
areolar spaces are confluent: in the centre of the interambulacral 
areas is a depressed space, which is filled with small close-set 
granules: the mouth-opening is very large, and that for the 
apical dise is so likewise: the spines taper gently from the 
shoulder to their apex; they are round, and sculptured with 
longitudinal lines; their absolute length is not determinable, as 
neither of those before us are perfect; they may have attained 
the length of the diameter of the test. 
Affinities and differences.—We know so few true Cidarites 
from the tertiary rocks, that materials for comparison fail us. 
The only species we possess is the C. Alabamensis, Morton, from 
the tertiaries of the U. States, which has nearly straight am- 
bulacra, ten tubercles in each row in the interambulacra, with 
wide intertubercular spaces between each pair of rows. The 
Maltese Urchin differs essentially from this species, and may be 
easily distinguished from it by the concave ambulacral areas, and 
the marginal rows of tubercles that define these portions of the 
test. It is somewhat remarkable that we should have discovered 
so few Cidarites in all the Urchin beds that have been so dili- 
gently explored in the tertiary beds of Europe. 
Locality and stratigraphical range.—This species has been 
found only in bed No. 1, the Gozo marble, where it is rare. 
Echinus Duciei, Wright. PI. IV. fig. 2 af. 
Test circular, much depressed : ambulacral areas more than half 
the width of the interambulacral, with two rows of marginal, 
nearly equal-sized tubercles throughout, and two other rows 
within these, extending from the border to the mouth ; one of 
these inner rows ascends a short way above the border : inter- 
ambulacral areas with eight rows of tubercles at the border, 
diminishing to two rows abuve the others, disappearing or 
becoming of secondary size ; from the border to the mouth, 
the eight rows continue of uniform size: the pores are in 
triple oblique pairs ; between each pair there is a slight ridge 
of the test, which gives a singular zigzag figure to the pori- 
ferous avenues : mouth large and decagonal, base flat : apical 
dise of moderate size, but not preserved. 
Dimensions —-Height 33ths of an inch; transverse diameter 
132 inch. 
Description —This beautiful Urchin has been thought to be 
identical with the H. Sczlle, Desmoul., and the one figured by 
Scilla in pl. 138. fig. 1, pl. 25. fig. 1, and pl. 26. fig. A, B, of 
his work* ; but the number of tubercles on each of the plates 
* De Corporibus Marinis Lapidescentibus. 
