CRETACEOUS ECHIXODERMATA. 47 



he redescribed and now for the first time figured the same form as Cidarites armiger, a name which 

 he stated he desired substituted for C. splendens. Gabb in 1859 employed both names, mistaking 

 them for independent species, but refers to C. splendens as C. splendens. The specimens exam- 

 ined by the miter were chiefly detached plates, although one nearly complete test and two entire 

 or nearly entire interambulacral areas, with parts or all of the adjoining ambulacra, were also 

 among this material. In these specimens the oral side is slightly more depressed than the aboral, 

 although not to the extent exhibited in Morton's figure. The ambulacral areas, which are nar- 

 row and flexuous, have, between the poriferous avenues, four granules. In the center of each 

 column of plates these granules are approximately of equal size, the outer rows slightlv larger 

 but toward the disk or toward the peristome the inner rows abruptly diminish in size and finally 

 disappear. The pores are oval in shape with funnel-like openings exteriorly. Each row of 

 pores is separated from that which accompanies it in the same avenue by a row of imperfectly 

 defined granules that form an undulating ridge. 



The interambulacral areas are very wide and bear large tubercles, each of which covers 

 the greater portion of its plate. Upon the larger plates, in the center of each column, the 

 areolas are circular, but become somewhat oval toward both disk and peristome. The outer 

 edge of each areola is surrounded by a circle of large granules that give it a crenulated appearance. 

 The areola rises from its depressed margin, gradually at first, then rapidly, to the boss, which 

 reaches a marked elevation above the general level of the plate. The boss is of moderate width 

 and smooth. From its center rises the mamelon, which is small, perforated, and slightly 

 flattened upon the upper surface. The miliary space is covered by small granules, which are 

 most numerously developed along the median line of the interambulacra. 



None of the specimens affords the apical system. Strong auriculae show the presence of 

 powerful jaws. 



The spines are slender, elongated, cylindrical, with longitudinal, serrated ribs that gradually 

 become obsolete toward the base. The collar is short and finely striated longitudinally. The 

 acetabulum is bordered by a smooth margin and is perforated in the center. 



Related forms. — In many particulars Cidaris splendens (Morton) resembles C. serrata Desor« 

 of the European Cretaceous, but differs from it m several others notably in having oidy four 

 rows of granules between the poriferous avenues. 



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



Geologic horizon. — Vmcentown sand of the Rancocas group, Upper Cretaceous. 



Collections. — Philadelphia Academy of Natural Sciences; Johns Hopkins University 

 (T3002). 



Cidaris dixiensis Cragin. 



Plate IX, figures 7a-b. 



Cidaris dixiensis Cragin, 1893, Geol. Survey Texas Fourth Ann. Rept., p. 146. PI. XLVI, figs. 15, 16. 



Determinative characters. — Cragin says: 



Test rather small, thin; tubercles perforate, not crenulate, rather small and feebly elevated; areolae feebly depressed; 

 interambulacral plates ornamented with crowded rounded granules which increase in size (in the smaller plates, °rad- 

 ually) toward the areola, the largest granules forming an alternating double row around it. 



Dimensions. — Height of interambulacral plates 6 to 7 milUmetei-s; width 7 to 8 millimeters. 



Descri.ption. — The isolated interambulacral plates, which are the only portions of the test 

 known, indicate that the form was not in all probability a large one. The tubercles are but 

 slightly elevated, and the areoise are feebly depressed. The mamelon is small and perforated. 

 The boss is smooth. The miliary space is relatively narrow, covered with granules larger toward 

 the areola, where they form an alternating double row around it. ' 



Related forms. — The characters given separate this species from all of the American species with which the writer 

 is acquainted. In the fades of the interambulacral portion of the test, it bears considerable resemblance to C. serrijer 

 Forbes, from which it differs in the form of the plates. 



Locality. — Nine miles northeast of Dallas, Tex. 



Geologic horizon. — Taylor marl, Upper Cretaceous. 

 Collection. — Geological Survey of Texas. 



