ii.AKK.j PEDIXOPSIS J'ONDI. 57 



PEDTNOPSIS Cottoaii. 



Pedinopsis Pondi (^lark. 



Plato XXI, Fi,us. la-h. Plate xxri, Fif^s. \a-<'. 



Determinative chamctcr.s. — Test large, circular, inllated at the sides, 

 convex on the upper surface. Anibulacia with six rows of tu])ercles at 

 the ambitus, the two uiariiinal rows complete and the four inner incom- 

 plete; poriferous zones broad, bigeminal. Interambulacra with twenty 

 rows of tubercles at the ambitus, Avhich become reduced to four at the 

 margin of the mouth opening; tubercles small, eqiuil, crenulated, and 

 perforated. Mouth opening small, w'itli distinct incisions. 



Dimensions. — Transverse diameter, 3^ inches; lieiglit, 2^ inches. 



Description. — The single very large specimen of this species exam- 

 ined by tlie waiter has portions of the test in a very perfect state of 

 preservation. The test is l?irge, circular, inllated at the sides, and con- 

 vex on the upper surface. The lower surface is flattened, with a slight 

 concavity in the region of the mouth opening (PI. xxii, Fig. la). The 

 ambulacral areas are wide, and have at the ambitus six rows of tuber- 

 cles (PI. XXII, Fig. Ic), the two marginal rows alone continuing from the 

 discal oi>ening to the peristome. The four inner row\s are incomplete, 

 but of equal size with the outer. The tubercles are finely crenulated 

 and perforated. The poriferous zones are broad and bigeminal (PI. 

 XXII, Fig. Ic), except on the lower surface, where the rows become 

 crowded together. Near the mouth opening they again broaden out 

 and become greatly increased in number at the margin. The pores 

 are small and round. The interambulacral areas are broad and have 

 twenty rows of tubercles at the ambitus, which become reduced to fimr 

 at the mouth edges (PL xxii, Fig. lb). The tubercles are of equal size 

 with those of the ambulacra. Small mammillated granules are found 

 scattered over both the ambulacral and interambulacral plates, to- 

 gether with a fine granulation covering the entire surfoce. 



The mouth opening is small and measures about seven-eighths of an 

 inch in diameter. It has ten distinct incisions in the interambulacra. 

 The discal opening is partially outlined, but is very indistinct. 



This species is named for Mr. Edwin J. Pond, of the U. S. Coast and 

 Geodetic Survey, by whom the specimen described by the Avriter was 

 discovered. 



Related forms. — The present species is unlike any described from 

 American or European deposits. 



Loealiti/ anil (leohxjk-al horizon. — The specimen was found on the south 

 bank of Onion creek, Travis county, Texas, about one-fourth mile south- 

 west of the crossing of the Austin and San Antonio wagon road. It is 

 probably from the lower portion of the Austin chalk (upper Cretaceous). 



Collection. — Johns Hopkins University. 



