(tt Dr. T. Wright on Fossil Echinodcrms 



areolar spaces arc 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 disc 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 a-f. 



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 above 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 

 disc of moderate size, but not preserved. 



Dimensions. Height Mths of an inch ; transverse diameter 

 Hi inch. 



Description. This beautiful Urchin has been thought to be 

 identical with the E. Scilla, Desmoul., and the one figured by 

 Scilla in pi. 13. fig. 1, pi. 25. fig. 1, and pi. 26. fig. A, B, of 

 his work * ; but the number of tubercles on each of the plates 



* De Corporibus M arinis Lapidescentibus. 



