46 MESOZOIC AND CENOZOIC ECHINODEKMATA OF THE UNITED STATES. 



Description. — The fragments of this form examined are sufficiently distinctive to separate 

 it from other species. A nearly complete interambulacrum with the adjoining ambulacra 

 shows that the test of the species is small and in a marked degree inflated. 



The ambulacra are narrow, slightly sinuous, and provided with four nearly equal rows of 

 granules between the poriferous avenues. On some additional granules are irregularly inter- 

 spersed. 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. 



The interambulacral plates are moderately large. On account of the indistinctly marked 

 sutures the small tubercles and numerous granules cause a very even surface over the entire 

 interambulacrum. The tubercles are circular and stand nearer the outer margin of the plates 

 than the inner. The areolas are deeply depressed, the central portion but slightly exceeding the 

 margin in height. The boss is smooth and stands but little above the level of the plate. The 

 mamelon is imperforate. The wide nhliary space is covered with a large number of irregularly 

 arranged granules of equal size. The broken specimens afford no information as to the character 

 of the apical system or peristome. 



Related forms. — The species is very readily separated from C. splendens, the only other 

 representative of this genus thus far reported from the Atlantic coast Cretaceous, by its pos- 

 session of imperforate mamelons and wide miliary spaces, over which the granules are regularly 

 scattered. The even surface of the test is likewise a distinguishing feature. 



Localities. — Timber Creek. (type) and Vincentown, N. J. 



Geologic horizon. — Vincentown sand of Rancocas group, Upper Cretaceous. 



Collection. — Academy of Natural Sciences of Philadelphia (1451 ) ; Johns Hopkins University. 



ClDAEIS SPLENDENS Morton. 



Plate IX, figures 4a-b, 5a-f, 6. 



Cidaris (?) sp. Morton, 1829, Acad. Nat. Sci. Philadelphia Jour., 1st ser., vol. 6, p. 123. 



Echinus sp. Morton, 1830, Am. Jour. Sci., 1st ser., vol. 17, p. 287; vol. 18, PI. Ill, figs. 12, 13. 



Cidarites splendeus 1 Morton, 1841, Acad. Nat. Sci. Philadelphia Proc, vol. 1, p. 132. 



Cidarites armiger Morton, 1842, Acad. Nat. Sci. Philadelphia Jour. , 1st ser., vol. 8, p. 215, PI. II, fig. 1. 



Cidaris armiger Gabb, 1859, Cat. Invert. Fossils Cretaceous formation, p. 18. 



Cidaris splendens Gabb, 1859, Cat. Invert. Fossils Cretaceous formation, p. 18. 



Cidaris armigera Agassiz, 1874, Revision of the Echini, p. 751. 



Cidaris armiger Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 75. 



Cidaris splendens Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 51. 



Cidaris splendens Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 33-35, PI. VI, figs. 3a-g. 



Cidaris splendens Johnson, Acad. Nat. Sci. Philadelphia Proc, vol. 57, p. 6. 



Cidaris splendens Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 279-281. 



Determinative characters. — Test of moderate size, spheroidal. Ambulacral areas narrow, 

 flexuous, with four rows of granules between the pore pairs, the outer rows larger than the inner; 

 imperfectly defined granules also appear between the pores of each pair. Interambulacral areas 

 very wide, with seven or eight plates in each column, each plate bearing a tubercle of large size 

 characterized by a wide circular areola, smooth boss, and small perforated rnamelon. Miliary 

 area small and covered with numerous thickly set granules of small size. Sutures sharply 

 defined, depressed. Spines elongated, cylindrical, with longitudinal rows of sharp denticulated 

 processes. 



Dimensions. — Height 21.9 to 23 millimeters; width 34.4 to 40 millimeters. 



Description. — The first mention of this form is made by Morton in 1829, when he doubtfully 

 referred a few fragments to Cidaris without an attempt at specific determination. Several of the 

 more important characters were then given, but as the material examined included only detached 

 plates and a few spines the description necessarily lacked much of completeness. In 1841 he 

 proposed the name Cidarites splendens and then more accurately defined the species. In 1842 



1 Morton doubtless intended to use the term splendens instead of splendeus, which is probably a typographic error. In the publication of 

 . 1842, where armiger is substituted, the form splendens is used. 



