28o CRETACEOUS PALEONTOLOGY. 



1893. Cidaris splendens Clark, Bull. U. S. G. S., No. 97, p. 33, 



pi. 6, fig-s. 3 a-g. 

 1905. Cidaris splendens Johns., Proc. Acad. Nat. Sci. Phil., 



1905, p. 6. 



Description. — Test of moderate size, spheroidal, the oral side 

 slightly more depressed than the aboral. Ambulacral areas nar- 

 row, flexuous, with four rows of granules between the pore pairs, 

 in the center of each column of plates these granules are approxi- 

 mately of equal size, the outer rows slightly larger, but towards 

 the oral and aboral extremities the inner rows rapidly diminish 

 in size and finally disappear; the pores are oval in shape, with 

 funnel-like openings exteriorly, imperfectly defined granules 

 forming an undulating ridge are present between the pores of 

 each plate. Interambulacral areas very wide, with seven or eight 

 plates in each column, each plate bearing a tubercle of large size 

 characterized by a wide areola, smooth boss and small perforated 

 mamelon, upon the larger plates in the center of each column the 

 areolas are circular, but they become somewhat oval towards the 

 oral and aboral extremities; the outer margin of each areola is 

 surrounded by a circle of large granules that give it a crenulated 

 appearance; the margin itself is depressed, and rises gradually 

 at first, and then rapidly, to the boss which reaches a marked 

 •elevation above the general level of the plate. The miliary area is 

 ■small and is covered with small, crowded granules that are more 

 numerously developed along the median line of the interambu- 

 lacra. The sutures are sharply defined and depressed. The spines 

 are slender, elongated, cylindrical, with longitudinal, serrated 

 ribs that gradually become obsolete towards the base, the collar 

 is short and finely striated longitudinally; the acetabulum is 

 bordered by a smooth margin and is perforated in the center. 



The dimensions of a complete individual are: height, 21.9 

 mm. ; width, 34.4 mm. 



Remarks. — This species usually occurs in the form of detached 

 plates, occasionally all or a part of one or more of the meridional 

 areas are found still joined together, and Morton has illustrated 

 a nearly complete example. The apical system of plates has in 

 no case been observed. The species is similar to C. serrata Desor., 



