130 University of California Publications in Geology [Vol. 12 



of both pairs of lateral petals bent slightly backward as in other 

 related forms. Poriferous zones moderately wide ; interporiferous 

 areas broad, being about three or four times the width of the porif- 

 erous areas. Pores oval and conjugated. Actinal surface faintly 

 concave. Indistinct, broad anibulacral furrows extend from the mouth 

 to near the margin ; poorly developed broad lines branch off from 

 the main furrows less than half way to the edge. Both surfaces are 

 covered by numerous prominent perforated tubercles which are sur- 

 rounded by wide granular scrobicules ; the tubercles are regularly 

 spaced and of the same size, except those situated on the poriferous 

 zones and those close to the apical system, which are smaller. Spines ' 

 slender, covered with granules, arranged in longitudinal rows; these 

 have a heavy base to fit the large mamelon of the tubercle. Peristome 

 small, subcircular, posteriorly eccentric, and situated opposite the 

 apical system. Periproct circular and inframarginal to almost mar- 

 ginal. 



Related forms. — Denelraskr perrini is very closely related to D. 

 coalingaensis Twitchell and D. arnoldi Twitehell, from which it differs 

 mainly in having a much thicker test and tubercles which are of 

 uniform size over the surface. 



Geologic horizon. — Upper Etehegoin and Purisima formations. 

 Upper Pliocene. Associated with Dendraster gihbsii var. humilis Kew 

 and D. arnoldi Twitchell. 



Localities. — Holotype from near Coalinga, California (Weaver) ; 

 figured specimen no. 11018 from Coalinga district, Fresno County, 

 California ; Zapato Creek, one-half mile south of A. Kreyenhagen 's 

 place Coalinga district, California (U. S. Geol. Surv. ) ; also reported 

 from San Gregorio, California. 



CALASTER Kew, n. subgenus 



Dendraster. In part, Clark and Twitchell, Mesozoic and Cenozoic Echino- 

 dermata of the United States, U. S. Geol. Surv. Mon., vol. 54, 1915, 

 p. 190. 



The subgenus Calaster is used here to include all dendraster-like 

 forms having a distinctly supramarginal periproct. 



