40 MESOZOIC ECHINODERMATA OF THE UNITED STATES. [bull. 97. 



Test spheroidal or depressed. Ambulacral areas narrow, straight 

 orflexuous; poriferous zones narrow; pores round, uuigeminal, often 

 increased in number toward the mouth opening. luterambulacral areas 

 broad, with two rows of primary tubercles. Apical disk large and 

 prominent. Mouth opening large, with incisions at regular intervals. 

 Anal opening eccentric. 



SALENIA Gray. 



Salenia texana Credner. 



Plate X, Figs. la-h. 



Cidaris diatretum Giebel, 1853. Jaliresber. d. Naturw. Vereins in Halle, 1852, p. 374, 



PI. 7, Fig. 2. 

 Salenia texana Credner, 1875. Zeitsohr. f. d. Ges, Natiirw., xi-vi, pp. 105-116, PI. V, 



Figs. 1-6. 

 Salenia texana Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 75. 



Determinative characters. — Test subglobose; upper surface convex; 

 sides inflated ; under surface flat. Ambulacra narrow, flexuous, with 

 two rows of manimillated granules in each area: poriferous zones flexed; 

 pores unigeminal. luterambulacral areas wide, with two rows of alter- 

 nating plates, six in each row. Apical disk large, convex, subcircular; 

 anal opening prominent. Mouth opening moderately large. 



Dimensions. — Height, f inch; transverse diameter, 1 inch. 



Description. — Oredner in the Zeitschrift fiir die gesammten Natur- 

 wissenschaften zu Berlin for 1870 i^resents the first complete diagnosis 

 of a North American Mesozoic echinoid, in tlie detailed descriptions 

 accorded the present species. Its reference by Professor Giebel in 

 1852 to Cidaris diatretum {=Pseudodiadema diatretum) is shown from 

 the carefully prepared specimens to have been erroneous. 



The test is subspherical when complete, but in the specimens exam- 

 ined is generally somewhat flattened, both actinally and abactinally. 

 Tlie lower surface is slightly concave in the vicinity of the month open- 

 ing. The sides are inflated, presenting a rounded surface which is fuller 

 above than below (PI. x. Fig. Ic). 



The ambulacral areas are narrow, increasing gradually in width from 

 the apical disk to the mouth opening. Two rows of mammillated gran- 

 ules, twenty-four to twenty-six in each, occupy the middle of each area. 

 Very minute granules exteiul in a line between the rows and in the 

 vicinity of the mouth opening surround the larger granules themselves. 

 The poriferous zones are narrow and flexuous and the pores are regu- 

 larly arranged in a unigeminal series; near the mouth opening they 

 are slightly more crowded. The most pronounced flexure is opposite 

 the second, intcrambulacral plate from the apical disk. Toward the 

 mouth opening the zones become nearly straight (PI. x, Figs, le, 1/). 



