108 Dr. T. Wright on Fossil Echinoderms 



Description, — This is a very rare Urchin in the Maltese beds. 

 It has an oblately spheroidal figure, and is much depressed at 

 both poles ; the ambulacral areas, with the poriferous zones, are 

 gently undulated ; they measure together /jyths of an inch in 

 width; the areal band is depressed in the middle, and its 

 elevated margins are covered with two rows of large equal-sized 

 close-set granules ; internal to these are two rows of much smaller 

 granules, and down the centre is a depressed furrow : the pori- 

 ferous avenues lie likewise in depressions, bounded internally by 

 the marginal granules of the ambulacral areas, and externally by 

 the encircling granules of the primary tubercles : the inter- 

 ambulacral areas are 3 J times the width of the ambulacral ; they 

 form rather prominent convex portions of the test, with from 

 five to six rows of primary tubercles in each of the two rows of 

 these areas: the areolas are large and prominent, the summits 

 are smooth and without crenulations, and the tubercles, which 

 are proportionately large, and with a very small perforation in 

 their summit, stand well out from the body : a circle of larger 

 granules surrounds the base of the mammillary eminences; 

 these circlets are each complete in the two superior tubercles, 

 but one series is common to two tubercles in those near the 

 mouth ; the boundary in all, however, is defined, as none of the 

 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 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. 



