288 CRETACEOUS PALEONTOLOGY. 



Formation and locality. — Vincentown limesand, Timber Creek 

 (Clark). 

 Geographic distribution. — New Jersey. 



Family ECHINIDAB. 



Genus PsAMMECHiNUS Agassiz. 



Psammechinus cingulatus Clark. 

 Plate X., Figs. 1-9. 



1 89 1. Psammechinus cingulatus Clark, Johns Hopkins Univ. 



Circ, vol. 10, No. 87, p. 76. 

 1893. Psammechinus cingulatus Clark, Johns Hopkins Univ. 



Circ, vol. 12, No. 103, p. 51. 

 1893. Psammechinus cingulatus Clark, Bull. U. S. G. S., No. 



97, P- S5> Pl- 20, figs. I a-i. 

 1905. Psammechinus cingulatus Johns., Proc. Acad. Nat. Sci. 



Phil., 1905, p. 6. 



Description. — Test small, subhemispherical, with circular cir- 

 cumference, ventral side flattened, becoming somewhat concave 

 towards the oral opening, sides inflated, dorsal surface elevated 

 and moderately convex. Ambulacral areas wide, with 18 

 or 20 plates in each row; the lower 16 or 17 plates in each 

 row bear prominent tubercles that occur in a continuous line to 

 the peristome ; on each side of these primary tubercles is a smaller 

 one of similar shape, the inner one being situated towards the 

 upper angle of the plate and the outer one towards the lower 

 angle, besides these, several smaller tubercles or granules are 

 present upon each plate; poriferous zones depressed, trigeminal, 

 the three pore pairs of each plate arranged in semi-circular form, 

 the two upper pairs separated from the lower by the outer sec- 

 ondary tubercle. Inter-ambulacral areas about one and one-half 

 times as wide as the ambulacral with about 1 5 plates in each row ; 

 each plate with a large tubercle in the center, around which sev- 

 eral smaller ones of various sizes are irregularly arranged. The 

 tubercles of both ambulacral and interambulacral plates are sim- 

 ilar in form, with a large, elevated, non-crenulated boss and an 



