MIOCENE ECHIXODERMATA. 187 



Test subcircular in general outline, with deep, broad, marginal notches in the edges of the ambulacral areas. The 

 two posterior notches are much deeper than are the anterior ones, and truncate the posterior interambulacral space on 

 either side of the median line, shaping the posterior end of the test into a prominent process. The test when viewed 

 from above has a leaf-like appearance. Test much depressed, edges markedly thin, abactinal surface very slightly- 

 arched, apex central; actinal surface flat or gently concave. Mouth central, slightly sunken; ambulacral furrows 

 poorly shown in the specimens examined, but evidently branch but little, if at all. Main ambulacral grooves continue 

 from the mouth to the margin, entering the marginal notches. Anal pore small, inframarginal. Ambulacral star cen- 

 tral. Petals extend about three-fourths the distance to the margin and not entirely closed at the ends. 



Dimensiojis. — Longitudinal diameter, 55 millimeters. 



As only a single figure of this form is given by Pack, 1 and as that too is one of the under sur- 

 face of a weathered specimen, it is hardly possible to discuss the form intelligently. However, 

 it may be said that the marginal outline, with its five large ambulacral notches alternating with 

 broad, blunt, rounded projections differentiates the form from all other known Californian echi- 

 noids. From the description and figure the form appears to be a Scutella. The resemblance of 

 the present species to Astrodapsis whitneyi which Pack remarks upon in connection with his 

 description of A. antiselli is but a slight one, as the notches of A. whitneyi are not nearly as large. 



Localities. — Five miles northwest of the Stone Canyon coal mine, Monterey County, and at 

 San Juan River near La Panza, San Luis Obispo County, Cal. 



Geologic horizon. — Vaqueros formation, lower Miocene. 



Collection. — University of California. 



Scutella aberti Conrad. 



Plate LXXXVI, figures la-b; Plate LXXXVII, figures la-d. 



Scutella aberti Conrad, 1842, iSat. Inst. Promotion Sci. Proc, 2d Bull., p. 194, no figure. 



Scutella alberti Bronn, 1S4S, Index palteontologicus, vol. 1, p. 1125, vol. 2, p. 196. 



Scutella alberti Meek, 1864, Smithsonian Misc. Coll., vol. 7 (183), p. 2. 



Scutella alberti Dall, 1892, IT. S. Geol. Survey Bull. 84, p. 52. 



Scutella aberti Clark, 1904, Maryland Geol. Survey, Miocene, p. 432, PL CXXIX, figs. 2, 2a, and PL CXX, figs, la, 



lb, 2a, 2b. 

 Scutella aberti Clark, 1906, Maryland Geol. Survey Rept., vol. 6, p. 258, PL XXII, fig. 17. 

 Scutella aberti Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 705. 



Determinative characters. — Test large to very large, subcircular to subquadrate in marginal 

 outline, the whole form much depressed, less so within the large petaloidal area where it rises in 

 the form of a low, broad mound whose flattened summit is excentric anteriorly, margin relatively 

 thin, with three large, broad notches in the posterior border, between which the test extends in 

 the form of two large, broad, blunt projections; under surface flat. Ambulacral petals very 

 large, subspatulate, extending more than two-thirds the way to the margin. Apical system 

 slightly excentric anteriorly but less so than the apex. Peristome small, subpentagonal, ambu- 

 lacral furrows simple and straight for a short distance from the peristome, then forking, the 

 branches proceeding somewhat sinuously and divergingly to the margin. Periproct very small, 

 subcircular, inframarginal, near the head of the pointed central notch in the posterior border. 



Dimensions. — Length 120 millimeters; width 121.5 milhmeters; height 14 millimeters. 

 The largest specimen examined was 178 milhmeters in diameter. 



Description. — This species, the largest of American Scutellas, was first reported in 1S42 by 

 Conrad, who described but did not figure it, and who named it after Col. J. J. Abert, of Washing- 

 ton, D. C. It was first figured by Clark in 1904. The form has been but little known owing to 

 its limited distribution and to the obscure and out of the way character of the publication in 

 which Conrad's description was published. Perfect specimens are rare; imperfect ones and 

 fragments are very abundant in the thin bed in which it occurs and to which it appears to be 

 restricted. It is not known positively to occur outside of Maryland. Several authors have 



1 Since the above description was written Pack has published additional details regarding S. norrisi, based on recently discovered material 

 (Univ. California Dept. Geology Bull., vol. 7, No. 13, pp. 299-300, PI. XV, fig. 1). The new material establishes on firm foundation this new 

 species, which is unlike all other California scutellid forms. 



