38 MESOZOIC ECHINOr>ERMATA OF THE UNITED f^TATES. [bull. 97. 



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 interambulacral area (PI. VI, 

 Fig. 4:1)). 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 mame- 

 lon is imperforate (PI. vi. Fig. 4:d). The wide miliary space is covered 

 Avith a large number of irregularly arranged granules of equal size. 

 The broken specimens afford no information as to the character of the 

 apical disk or mouth edges. 



Related forms. — This species is very readily separated from C. s])len- 

 dens, tlie only other representative of this genus thus far reported from 

 the Atlantic Coast Cretaceous, in possessing imperforate mamelons 

 an'd wide miliary spaces, over which the granules are regularly scat- 

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



Locality and (jeologieal horizon. — The specimens of this form examined 

 by the Avriter were found associated with C. splendens in the yellow 

 limestone of the middle marl bed (upper Qpetaceous), of Timber creek. 

 New Jersey. 



Collection. — Philadelphia Academy of Natural Sciences. 



LEIOCIDARIS Desor. 



Leiocidaris hemigranosus (Shumard). 



Plate VII, Figs. 2a-d. Plate viii, Figs. Ici^h. Plate ix, Fig. la-c. 



Cidarh hemigranosus Shumard, 1860. St. Lonis. Acad. Sci. Trans., vol. 1, p. 609. 



Cldaris hemigranosus Meek, 1864. Smith? Misc. Coll. (vol. 7, 177), p. 2. 



Cidaris hemigranosus White, 1883. U. S. Geo), aud Geog. Surv. of the Territories, 12th 



Ann. Kept, for 1878, p. 38, PI. 18, Figs. 2a-b. 

 Leiocidaris hemigranosus Clark, 1891. Johns Hopkins University Circulars, No. 87, 



p. 75. 



JDeterminative characters. — Test very large, ^subspherical. Ambula- 

 cral areas narrow, sinuous, with six rows of granules in the middle. 

 Poriferous avenues wide, deeply depressed. Pores of each pair united 

 by clearly defined furrow. Interambulacral areas broad. Tubercles 

 very large; areola circular or slightly polygonal, depressed; boss 

 smooth ; mamelon large, perforated. Miliar,y space covered with large 

 scattered oval granules. Sutures clearly marked, depressed. 



Dimensions. — Height, 2^ inches; width, 3f inches. 



Description. — This form, which was quite fully described by Shumard 

 in 1860, but not figured, was incorrectly referred to the genus Cidaris, 



