CRETACEOUS ECHINODEKMATA. 51 



The peristome is small, occupying scarcely two-fifths of the diameter of the test. Ten 

 incisions divide the edge into lobes, the ambulacral lobes projecting the farther. 



Related forms. —The identity of this species is readily established by the straight poriferous 

 zones and peculiar decorations of the apical system. The number of mammillated granules in 

 the ambulacral areas is less than in S. texana, and the oval granules of the interambulacral areas 

 are readily distinguishable from the round forms of S. bellula, The periproct also projects far 

 less than in S. texana, although in this respect it is not unlike S. bellula. 



Locality. — Timber Creek, near Vincentown, N. J. 



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



Collections.— Academyof Natural Sciences of Philadelphia (1448); Johns Hopkins University. 



Salenia bellula Clark. 



Plate XIII, figures 2a-g. 



Salenia bellula Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 75. 

 Salenia bellula Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 51. 

 Salenia bellula Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 43, 44, PI. XI, figs. 2a-g. 

 Salenia bellula Johnson, 1905, Acad. Nat. Sci. Philadelphia Proc, vol. 57, p. 6. 



Salenia bellula Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 283-284 PI VIII 

 figs. 11-17. 



Determinative characters. — Test small, compressed, circular; upper surface convex- sides 

 inflated; under surface flat. Ambulacra rather broad, nearly straight, with two rows of gran- 

 ules in each row; poriferous zones broad, very slightly flexed; pores round, uniserial. Interam- 

 bulacra wide. Apical system convex and nearly circular. Peristome small. 



Dimensions. — Diameter 6 to 8 millimeters ; height 10 to 13 millimeters. 



Description. — This Salenia is a very rare form, only a few specimens having come under the 

 notice of the writer. Certain peculiarities of outline and structure prevent its being confounded 

 with other species heretofore described. 



In general outline the test is somewhat flattened; the upper surface is regularly convex; the 

 sides are inflated; the lower surface is flat or shghtly concave at the peristome. 



The ambulacra are prominent and change but shghtly in width from the apical system to 

 the peristome. Two rows of mammillated granules, 15 in each, occupy the center of each 

 area. 



The interambulacra are wide and consist of two rows of alternating plates, five or six in 

 each. The tubercles are prominent, but decrease rapidly in size, the boss narrow and indistinctlv 

 crenulated, and the mammalon small, flattened, and imperforate. An indistinct circle of mam- 

 millated granules surrounds each tubercle. They unite to form a sinuous double series between 

 the rows of tubercles. Between the larger granules are scattered irregularly numerous small 

 granules that are crowded together along the central line of the interambulacra. 



The apical system is shghtly convex, the periproct interfering but little with the regularity 

 of the curved surface. The periproct is subcircular, with a flangelike rim. The plates are 

 decorated with oval granules arranged in radial rows extending from the opening of each genital 

 plate and unite with corresponding rows of adjacent plates at the suture. 



The peristome is small, being one-third of the transverse diameter of the test. Ten weak 

 incisions divide the edge into lobes that are nearly of equal size. 



Related forms. — This species is quite distinct from Salenia texana or S. tumidula, and at the 

 same time does not admit of reference to any of the European species. It is most closely related 

 to S. tumidula, but is more compressed, has a cliff erently shaped and decorated apical system, and 

 has round and mammillated granules in the miliary space, whereas those of S. tumidula are char- 

 acteristically oval. 



Locality. — Timber Creek, near Vincentown, N. J. 



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



Collections. — Academyof Natural Sciences of Philadelphia (1446); American Museum of 

 Natural History, New York. 



