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University of California Puhlicatiom in Geology [Vol. 12 



height 17 mm. Marginal outline suboval to subeircular, with indis- 

 tinct notches in the posterior ambulacra and a slight lobing of the 

 odd interambulaeral area. Upper surface considerably depressed, but 

 regularly arching to a low apex, which is usually a short distance 

 anterior to the center of the test ; interambulacra markedly grooved 

 from the apical system to the edge of the test ; shallower grooves are 

 present along the sides of the petals in the ambulacral areas. Apical 

 system central. Petals elevated and extending nearly to the margin. 

 Inner rows of pores diverge at first and tlien continue in approxi- 

 mately parallel lines until close to the edge of the test, when they 

 again diverge slightly ; outer rows diverge to a greater degree at first 

 and then converge slightly to the point where the inner rows start 

 to diverge for the second time, and continue parallel to the latter 

 from this point to the margin. In some specimens the inner rows may 

 converge slightly. Poriferous areas narrow, each being about one- 

 fourth the width of tlie interporiferous area. Actinal surface concave. 

 Peristome central, large, and circular in outline ; slightly sunken. 

 Ambulacral furrows deep near the peristome, becoming indistinct near 

 the margin, and then passing into lines which usually extend over 

 the upper surface nearly to the apical system as median lines on the 

 petals ; faint lines are given off from the main furrows when slightly 

 over half the distance to the margin, and these continue over the 

 upper surface as sutural lines between the ambulacral and interam- 

 bulaeral plates. Periproct relatively small, sunken, and with the 

 immediate area surrounding it somewhat swollen. Numerous scrobicu- 

 lar tubercles are of the same size on both surfaces, except in the 

 depressed portions of the abactinal side, where they are smaller. 



Related forms. — This form is closely related to the other members 

 of the Astrodapsis arnoldi group, but may be distinguished by its 

 relatively large peristome, by the posterior lobing in the odd inter- 

 ambulaeral area, and by its comparatively narrow petals with the rows 

 of pores in approximately parallel lines. 



Geologic horizon. — Lower Etchegoin (Jacalitos) formation. Lower 

 Pliocene. 



Localities. — Holotype from south of Pancho Rico Creek in NW. I/4 

 of Sec. 8, T. 22 S., R. 11 E., Univ. Calif., loc. 3127; also occurs at 

 Lynch Creek, Salinas Valley district, Monterey County, California. 

 A small form of this species occurs at a locality on the Hog Canyon 

 road. Sec. 7, T. 24 S., R. 14 E., Monterey County, California. 



