Vol. 5] Pack. — Tertiary Echinoids of California. 



281 



close relationship exists between Astrodapsis antiselli and Astro- 

 dapsis tumidus, and it is probable that the latter should be con- 

 sidered only as a variety of the former species. Astrodapsis 

 xvhitneyi has evidently been confused with one of the variations 

 of Astrodapsis tumidus. The original description apparently re- 

 fers to a form which appears in the uppermost San Pablo in 

 Contra Costa Comity, and also in the upper Miocene (the Santa 

 Margarita formation of Arnold) near Coalinga. Tins form 

 shows some resemblance to the new form Scutella ( t) norrisi from 

 Stone Canon, especially noticeable in the prominent posterior 

 ambnlacral notches. 



ECHINARACHINUS EXCENTRICUS Eschseholtz. 



1826. Scutella excentricus Eschseholtz, Zool. Atlas, pi. 20, fig. 2. 

 1846. Echinarachinus excentricus Eseh. Valenciennes, Voyage Venus, pi. 10. 

 1856. Scutella striatula Conrad, Pae. R. E. Repts., vol. 7, pi. 9, figs, la, b, 

 and 2. 



1873. Echinarachinus excentricus Eseh. Agassiz, Mus. Comp. Zool. Harv. 



Univ., Mem. 3, pp. 107, 524; pi. 13a, figs. 1-4. 

 1888. Echinarachinus excentricus Eseh. (Cooper) Cal. State Mm. Bur.; 7th 



Ann. Rep. State Mineralogist, p. 271. 



1898. Echinarachinus excentricus Eseh. (Merriam) Univ. Calif. Publ. Geol., 



vol. 2, p. 110. 



1899. Echinarachinus excentricus Eseh. (Merriam) Proe. Cal. Acad. Sci., 



3rd ser., Geol., vol. 1. p. 170; pi. 22, fig. 8. 

 1903. Echinarachinus excentricus Eseh. (Arnold) Cal. Acad. Sci. Mem., vol. 

 3, p. 91. 



1907. Echinarachinus excentricus Eseh. (Arnold) U. S. G. S. Bull. 322, pi. 

 24, fig. 8. 



Test sub-pentagonal to sub-circular in outline, slightly broader 

 than long; edges thin, frequently notched posteriorly. Vertex 

 slightly back of center of test, but well in front of eccentric api- 

 cal system. Ratio of distance from apical system to posterior 

 margin compared with distance from apical system to anterior 

 margin varies from 1 : 1.4 to 1 : 2.4. Upper surface of test slopes 

 up gently from margin to ends of petals, from here it forms a 

 regular arch. Actinal surface Hat with very slight tendency to 

 form a sunken mouth. Petals broad, open at the ends, very 

 unequal in size. Anterior petal straight, twice the length of the 

 posterior ones, with broad interporiferous space enclosed by nar- 



