184 MESOZOIC AND CENOZOIC ECHINODEEMATA OF THE UNITED STATES. 



the inner ends of the other petals, and the inner portion of the posterior interambulacrum; from 

 the median ridge the surface slopes at first steeply then gradually away to the side edges. The 

 under surface is slightly concave longitudinally. The apex is excentric anteriorly, at the highest 

 point of the median ridge. 



The ambulacral areas are rather narrow; the dorsal portions petaloid. The petals are 

 moderate in size, subelliptical, extending more than halfway to the margin, open at the ends, the 

 odd petal more widely open than the others. The poriferous zones are relatively wide, though 

 slightly less so than the interporiferous areas; pores oval, pairs of pores conjugated. 



The interambulacral areas are rather broad with the exception of the odd posterior area, 

 which is narrow. The surface of the test is covered with small uniform tubercles. 



The apical system is decidedly excentric anteriorly, about coincident with the apex. There 

 is a large, subcircular madreporite, four large genital pores, of which the anterior pair are some- 

 what nearer together than the posterior pair, and five small radial plates each perforated by a 

 minute pore. 



The peristome is excentric anteriorly. The character of the ambulacral furrows can not 

 be made out on the specimens studied. 



The periproct is very small, circular and supramarginal, almost marginal. 



Related forms. — S. andersoni is readily distinguished from all other American scutellas 

 by its longitudinally ridged upper surface, its longitudinally concave lower- surface, and its 

 pronounced marginal notches opposite the posterior paired petals. 



Localities. — West of Coalinga (Anderson), and Devils Den district, Kern County (figured 

 specimen), Cal. 



Geologic horizon. — Tejon formation, upper Eocene; Vaqueros sandstone, lower Miocene. 



Collections. — U. S. National Museum (165719); California Academy of Sciences. 



SCTJTELLA FAIRBANKSI Pack. 



Plate LXXXV, figures 4-6. 



IScutella gabbi Merriam, 1899, California Acad. Sci. Proc, 3d ser., Geology, vol. 1, No. 5, p. 168, PI. XXII, figs. 5, 5a. 

 Scutellafairbanksi(M.erria,m,M.S.) Arnold, 1907, U. S.Nat.Mus. Proc, vol. 32, p. 542, PI. XIII, fig. 3, PL XLIII, fig. 



3. No description. 

 Scutellafairbanksi Eldridge and Arnold, 1907, U. S. Geol. Survey Bull. 309, pp. 13, 17, 230, 232, PI. XXIX, fig. 3, 



PI. XXX, fig. 3. No description. 

 Scutellafairbanksi Pack, 1909, Univ. California Dept. Geology Bull., vol. 5, No. 18, pp. 276-277, PI. XXIII, fig. 1. 

 IScutella merriami Arnold, 1909, U. S. Geol. Survey Bull. 396, PL VI, fig. 4. Figure only. 



IScutella merriami Arnold and E. Anderson, 1910, U. S. Geol. Survey Bull. 398, PI. XXVIII, fig. 4. Figure only. 

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



Determinative characters. — Test medium in size; subcircular, transversely oval or broadly 

 subovate, slightly broader than long; margin markedly thin and faintly undulating, submarginal 

 area wide; the whole form greatly depressed, the upper surface rising gradually and very gentlv 

 from the margin to the low central' or subcentral apex; under surface flat or nearly so. Apical 

 system central or slightly excentric anteriorly and about coincident with the apex. Ambula- 

 cral petals relatively short, subequal in size, subsymmetrical as a group; the odd petal differing 

 from the rest in having its inner row of pores diverging gradually to the end, which is wide open, 

 much more so than in the other petals. Peristome central or subcentral; main ambulacral 

 furrows deep and probably simple and straight for most of the distance to the margin, then 

 branching. Periproct very small, supramarginal. 



Dimensions. — Specimen A (type): Length 53 millimeters; width 49 millimeters (Pack). 

 Specimen B: Length 33 millimeters; width 36 millimeters. 



Description. — This new Californian Scutella has a test which is of medium size, ranging 

 from about 1 to 2^- inches in diameter. In marginal outline it is somewhat variable, being 

 sometimes subcircular, sometimes transversely oval, sometimes broadly subovate. The margin 

 is markedly thin and faintly undulating, submarginal area wide. The whole form is greatly 

 depressed; the upper surface rising gradually and very gently from the margin to the low, central 

 or subcentral apex. The under surface is flat or nearly so. 



