ECHINODERMATA. 281 



from the European Cretaceous, but the American form differs 

 from the European in its smaller miliary areas and higher areolas, 

 also in the presence of only four rows of granules between the 

 poriferous avenues. It may be distinguished from the associated 

 C. walcotti by the perforated mamelons. 



Formation and locality. Vincentown limesand, Vincentown 

 (154), Timber Creek (Morton). 



Geographic distribution. New Jersey. 



Cidaris walcotti Clark. 

 Plate VII., Figs. 10-13. 



1891. Cidaris walcotti Clark, Johns Hopkins Univ. Circ., vol. 



10, No. 87, p. 75. 

 1893. Cidaris walcotti Clark, Johns Hopkins Univ. Circ., vol. 



12, No. 103. p. 51. 

 1893. Cidaris walcotti Clark, Bull. U. S. G. S., No. 97, p. 37, 



pi. 6, figs. 4 a-d. 

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



p. 6. 



Description. Test small, inflated. Ambulacral areas narrow, 

 slightly sinuous, with four nearly equal rows of granules between 

 the poriferous avenues, and at times with additional granules 

 irregularly interspersed; the poriferous avenues themselves are 

 narrow, deeply depressed, and slightly sinuous; the pores are 

 round with funnel-shaped openings produced by the intersecting 

 ridges ; these ridges, which separate the individual pores and the 

 pore pairs, give a lattice-like appearance to the poriferous zones. 

 Jnterambulacral areas broad, plates moderately large, with the 

 sutures indistinctly marked, and the small tubercles and numer- 

 ous granules giving them a very evenly marked surface; the 

 tubercles are circular and stand nearer the outer margins of the 

 plates than the inner; the areolas are deeply depressed, their 

 central portion but slightly exceeding the margin in height; 

 the boss smooth, standing but little above the level of the plate ; 

 the mamelon small, imperf orate; the wide miliary space covered 

 with a large number of irregularly arranged granules of nearly 

 uniform size. 



