MIOCENE ECHINODEBMATA. 197 



much less excentric apical system, its more symmetrically elliptical ambulacral petals, and the 

 fact that its posterior petals diverge less widely and also have poriferous zones which are less 

 widely divergent at their ends and more equal in length. Some specimens of D. arnoldi resemble 

 D. coalingaensis; but they have thicker margins, more widely open ambulacral petals, more con- 

 spicuous tubercles, more tumid interporiferous areas, and a central apex which is also not coin- 

 cident with the apical system. 



Localities.— Near A. Kreyenhagen's place (type), and 1,244-foot hill 4 miles southeast of 

 northwest end of Kettleman Hills, in Coalinga district, California. 



Geologic horizon.— Etchegoin formation (apparently limited to the upper portion of the 

 formation), upper Miocene and lower Pliocene ( I). 



Collection. — U. S. National Museum (165537). 



Dendraster sp. (Conrad). 



Scutella sp. Conrad, 1S57, U. S. Pacific R. R. ExpL, vol. 7, PL X, figs. 3, 4; no description. 

 Dendraster sp. Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 704. 



As Conrad gave no description of this form its exact relationships can not be determined 

 with certainty. It resembles Dendraster interlineatus in some respects, but not closely enough 

 to justify its identification with that species. 



Echinarachnitjs sp. Conrad. 

 Echinarachnius sp. Conrad, 1S57, U. S. Pacific R. R. ExpL, vol. 7, PL IX, fig. 5; no description. 



This is only a poor figure of an imperfect specimen, unaccompanied by a description. It 

 is not entitled to recognition and the exact relationships can not be determined from such data. 



Genus ASTRODAPSIS Conrad (amended). 



Astrodapsis Conrad, 1869, Acad. Nat. Sci. Philadelphia Proc, vol. 8, p. 315. 

 Astrodapsis Conrad, 1857, U. S. Pacific R. R. ExpL, vol. 7, Pal. Rept., p. 196. 

 Astrodapsis Remond, 1863, California Acad. Nat. Sci. Proc, vol. 3, p. 52. 



The writer does not agree with Duncan * in regarding Conrad's genus Astrodapsis as a 

 synonym of Breynius's genus Arachnoides. The inframarginal position of the periproct, 

 the depressed apical system, and the elevated ambulacral areas alternating with depressed 

 interambulacral areas sufficiently distinguish Astrodapsis from Arachnoides. 



Conrad's description of his genus is as follows: "Suboval; depressed; ambulacral areas 

 elevated or ridged; ambulacra nearly straight, widely open at the extremity; mouth central; 

 anus submarginal, beneath; radiating grooves as in Laganum." This description was good 

 in view of the small amount of material Conrad had, but it now becomes necessary to redraw 

 the diagnosis of the genus in order to make a few emendations. 



Description. — Test depressed, subdiscoidal to broadly subcorneal in general form, circular 

 to subelliptical in marginal outline, margin varying from thin to very thick, with or without 

 notches opposite the ambulacral petals. Ambulacral areas elevated or ridged; interambula- 

 cral areas depressed. Ambulacral petals straight, extending nearly to the margin, widely open 

 at the ends; poriferous zones nearly parallel, continuously diverging, or diverging, converging 

 and again diverging. Apical system more or less depressed. Peristome central or subcentral. 

 Main ambulacral grooves simple and straight from peristome to margin, continuing as fainter 

 grooves or processes over the margin and along the middle of the ambulacral ridges nearly to 

 the apical system ; two faint fines or processes are given off from the main grooves from one- 

 half to two-thirds the way to the margin, which continue over the margin and along the upper 

 surface between the tops of the ambulacral ridges and the bottoms of the ambulacral depres- 

 sions nearly to the apical system. Periproct small, inframarginal, almost marginal. 



1 Duncan, P. M., Revision of genera and great groups of the Echinoidea: Linn. Soc. Jour. Zoology, vol. 23, p. 165, 1891. 



