MIOCENE ECHINODERMATA. 201 



Localities. — Above Big Blue, west of Peerless Oil property, 9 miles north of Coalinga 

 (type), and Salinas Valley, Monterey County, Cal. 



Geologic horizon. — Santa Margarita formation, middle or upper Miocene. 

 Collections. — U. S. National Museum (165594); University of California. 



Astkodapsis whitneyi Reniond. 



Plate XCV, figures 2a-e. 



Astrodapsis whitneyi Remond, 1863, California Acad. Nat. Sci. Proc, vol. 3, p. 52; no figure. 



Astrodapsis whitneyi Meek, 1S64, Smithsonian Misc. Coll., vol. 7 (183), p. 2. 



Astrodapsis whitneyi Gabb, 1S69, California Geol. Survey Rept., Paleontology, vol. 2, pp. 37, 110, PI. XIII, figs. 67, 67a. 



Astrodapsis whitneyi Cooper, 188S, State Mineralogist of California Seventh Rept., p. 271. 



Astrodapsis whitneyi Merriam, 1899, California Acad. Sci. Proc, 3d ser., Geology, vol. 1, No. 5, p. 167, PI. XXI, figs. 



4, 4a. 

 non Astrodapsis whitneyi Arnold, 1909, U. S. Geol. Survey Bull. 396, p. 63, PL XI, fig. 1. See Astrodapsis arnoldi. 

 Astrodapsis whitneyi Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 703. 



Determinative characters. — Test medium to large; circular in marginal outline, broadly 

 subcorneal in general form; margin thin, with small subecmal ambulacral notches. Upper sur- 

 face rising directly from margin to the relatively high, slightly anteriorly excentric apex; with 

 high, narrow, steep-sided ambulacral ridges alternating with broad, deep interambulacral 

 depressions. Lower surface concave. Petals relatively narrow, elongate subelliptical, nearly 

 reaching margin, wide open at ends; inner rows of pores nearly parallel for most of their length. 

 Apical system slightly excentric anteriorly, faintly depressed below top of petals. Peristome 

 central; main ambulacral grooves simple, straight, and deep to the margin, continuing as faint 

 lines on upper surface nearly to apex; two faint processes given off about halfway to margin, 

 which also continue to and over margin and on upper surface nearly to apex. Periproct small, 

 subcircular, inframarginal, almost marginal. 



Dimensions. — Length 50 millimeters; width 50 millimeters; height 13 millimeters. 



Description. — This species was one of the first fossil echinoids to be reported from the 

 California Tertiary deposits, having been described, but not figured, by Remond in 1863. The 

 test is medium to large, ranging, according to Merriam, up to 65 millimeters in diameter. In 

 marginal outline it is circular; margin thin, with small but well-defined, subequal notches oppo- 

 site all the ambulacral petals. The whole form is depressed, but less so than in related species, 

 the upper surface being broadly subcorneal, rising directly from the margin to the relatively 

 high, slightly anteriorly excentric apex; with high, narrow, steep-sided ambulacral ridges alter- 

 nating with broad, deep, interambulacral depressions. The under surface is concave, the con- 

 cavity gradually deepening to the peristome, where it is about one-third of the height of the 

 test. 



The ambulacral areas are wide, wider than the interambulacral areas; dorsal portions 

 petaloid. The petals are relatively narrow, elongate subelliptical, long, nearly reaching the 

 margin; the poriferous zones are narrow, about half as wide as the tumid interporiferous areas, 

 the inner rows of pores elevated, nearly straight, and parallel for most of their length, wide apart 

 at the ends, composed of large, round openings; outer rows depressed, diverging for about half 

 the distance to the margin, then drawing near the inner rows, pores slitlike; pairs of pores con- 

 jugated; several pairs of pores occur beyond and diverge from the ends of the petals. 



The interambulacral areas at the margin are somewhat narrower than the ambulacral areas; 

 near the apex they are much narrower, almost obliterated; they are gradually depressed from 

 near the apex to the margin. The surface of the test is covered with small, inconspicuous 

 tubercles, varying in size and set in shallow scrobicules; the tubercles are somewhat larger in 

 the interporiferous areas than elsewhere. 



The apical system is slightly excentric. anterior^, faintly depressed below the tops of the 

 ambulacral petals. The details could not be made out on the specimen. 



The peristome is central. The main ambulacral grooves are simple, straight, and deep 

 from peristome to margin; they continue as fainter lines over the margin and along the middle 



