' i^HKi PSEUDODIADEMA TZXANUM. 47 



smaller tubercles, and between th^n minute granules. The poriferous 

 zones arc slij^litly tlcxcd, the pores of each plate being disposed in 

 curved form about the margin (I'l. xm, Fig. Id). Although there are 

 generally three pairs of pores on each plate, four pairs are not infre- 

 quent near the ambitus (PI. xm, Fig. Ir). 



The intoraml)ulacral areas are about one and one-half times the width 

 of the ambulacral, and have two rows of tubercles somewhat larger than 

 those of the latter. There are, in addition, several irregular rows of 

 secondary tubercles, of various sizes, that are most luimcrous between 

 the rows of primary tubercles and the poriferous zones. Sparsely 

 scattered over the interambulacral space are flattened granules (PI. 

 XIII, Fig. Ic). 



The primary tubercles of both the ambulacral and interambulacral 

 areas have wide circular areolas, elevated and dcei)ly crenulated bosses, 

 and distinctly perforated niamelons (PI. xm, Fig. 1/). 



The mouth opening is narrow, reaching scarcely one-third the diame- 

 ter of the test. The incisions of the margin are weak (PI. xiii, Fig. la). 



The discal opening is subpentagona;!. 



Related forms. — This species resembles in some particulars Pse»/Zo- 

 diadema ornntuM Goldfuss, of the (hetaceous of Europe, l)ut the latter 

 form has a different arrangement of the secondary tubercles and gran- 

 ules and lacks the radial striatiou upon the areolas. 



Locality and geokxjieal horizon. — Pseudodiadema diatrettim is fi'om 

 the yellow limestone of the middle marl bed (upper Cretacous) of Tim- 

 ber creek, l^ew Jersej^ 



Collections. — Philadelphia Academy of Natural Sciences; American 

 Museum of Natural History, New York. 



Pseudodiadema texanum (Roemer). 



Plate XIII, Figs 2a-b. Plate xiv. Figs. la-g. 



'Diadema texanum Koeiner, 1852. Die Kreidebildungeu von Texas, p. 82, PI. 10, Fig. 5. 



Pseudodiadema texanum Deaor, 1858. Synop. des fichinidcs fossiles, p. 72. 

 .Diadema texanum Gal)b, 1859. Cat. Invert. Fossils, Cretaceous, p. ID. 



Pseudodiadema texanum Meek, 1864. Smith Misc. Coll. vol. 7 (177), p. 2. 



Pseudodiadema Eoemeri Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 75. 



Determinative characters. — Test small, circular, depressed; sides in- 

 flated; upper and lower surfaces about equally flattened. Ambulacra 

 narrow, with two rows of i)rimary tubercles, eleven or twelve in each row ; 

 poriferous zones narrow, pores uuigeminal. luterambulacra wide, with 

 two lows of primary tubercles of larger size than those of the ambula- 

 cra. Mouth opening wide, covering nearly one-half the diameter of the 

 test. Discal opening siibcircular, with deep incision in right anterior 

 ambulacrum. 



Dimensions. — Transverse diameter, § inch; height, ys ineh. 



Description. — This form, descriljcd by Roemer,. in 1852, as Diadema 

 texanum, was assigned a new name (i*. Koemeri) by the writer in his 



