CEETACEOUS ECHINODERMATA. 65 



Pedinopsis pondi Clark. 

 Plate XXIV, figures la-d. 



Pedinopsis pond! Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 51. 



Pedinopsis pondi Clark, 1893, U. S. Geol. Survey Bull. 97, p. 57, PI. XXI, figs, la-b; PI. XXII, figs. la-c. 



Determinative characters. — Test large, circular, inflated at the sides, convex on the upper 

 surface. Ambulacra with six rows of tubercles at the ambitus, the two marginal rows complete 

 and the four inner incomplete; poriferous zones broad, biserial. Interambulacra with 20 

 rows of tubercles at the ambitus, which become reduced to four at the margin of the peristome; 

 tubercles small, equal, crenulate, and perforate. Peristome small, with distinct incisions. 



Dimensions. — Diameter 88 millimeters; height 58 niillinieters. 



Description. — The very large specimen on which this species is established has portions of- 

 the test in a very perfect state of preservation. The test is large, circular, inflated at the sides, 

 and convex on the upper surface. The lower surface is flattened, with a slight concavity in 

 the region of the peristome. 



The ambulacra are wide, and have at the ambitus six rows of tubercles, the two marginal 

 rows alone continuing from the discal opening to the peristome. The four inner rows are incom- 

 plete, but of equal size with the outer. The tubercles are finely crenulated and perforated. The 

 poriferous zones are broad and biserial, except on the lower surface, where the pore pairs become^ 

 crowded together. Near the peristome they again broaden out and become greatly increased 

 in number at the margin. The pores are small and round. 



The interambulacra are broad and have twenty rows of tubercles at the ambitus, which 

 become reduced to four at the peristome. The tubercles are of equal size with those of the 

 ambulacra. Small mammillated granules are found scattered over both the ambulacral and 

 interambulacral plates, together with a fine granulation covering the entire surface. 



The peristome measures about seven-eighths of an inch in diameter. It has 10 distinct; 

 incisions in the interambulacra. The discal opening is partly outlined but is very indistinct.. 



This species is named for Edwin J. Pond, of the United States Coast and Geodetic Survey,, 

 by whom the specimen described by the writer was discovered. 



Locality. — The south bank of Onion Creek, about one-fourth mUe southwest of the crossing; 

 of the Austin and San Antonio wagon road, Travis County, Tex. 



Geologic horizon. — Austin chalk, Upper Cretaceous. 



Collection. — Johns Hopkins University (T 3008). 



Subclass IRREGULARIA. 



Order GNATHOSTOMATA. 



Suborder HOLECTYPINA. 



Family PYGASTERID.E. 



Genus HOLECTYPTJS Desor. 



Holectypus planatus Roemer. 



Plate XXV, figures 2a-f, 3a-c, 4, Plate XXVI, figures la-e. 



Holectypus planatus Roemer, 1849, Texas, p. 393. 



Holectypus planatus Roemer, 1852, Die Kreidebildungen von Texas, p. 84, PL X, fig. 2. 



Holectypus planatus Shumard, 1852, Exploration Red River of Louisiana Rept., p. 211. 



Holectypus planatus Giebel, 1S53, Naturwiss. Ver. in Halle Jahresb., p. 373. 



Holectypus planus Giebel, 1853, idem. 



Holectypus planatus Conrad, 1857, U. S. and Mex. Boundary Survey Rept., vol. 1, pt. 2, p. 145, PL I, fig. 4. 



Holectypus planatus Desor, 1858, Synopsis des echlnides fossiles, p. 174. 



Holectypus planatus Gabb, 1859, Cat. Invert. Fossils Cretaceous, p. 18. 



Holectypus planatus Meek, 1864, Smithsonian Misc. Coll., vol. 7 (177), p. 2. 



