124 University of California Puhlications in Geology TVol. 12 



many irregular lines on their way to the margin. Periproct infra- 

 marginal, circular or subcircular, and situated about one or two milli- 

 meters from the margin. Surface covered by numerous small tubercles 

 situated in poorly developed scrobicules; uniform in size except near 

 the peristome, where tliey are larger. Structure of interior of test as 

 in Dendraster excentricus (Eschscholtz) , except that the radial parti- 

 tions do not extend so far in toward the center of the test. 



Related forms. — Dendraster gibbsii may be separated from D. ex- 

 centricus by its thicker test, more eccentric apical system, and by its 

 usually more widely divergent petals. From D. hesperis Kew it differs 

 in having the apical system more eccentric as well as the apex, the 

 angle between the posterior lateral petals is much greater, petals 

 extend nearer the margin with the bivium longer than the trivium, 

 the periproct is closer to the margin, and the peristome is more pos- 

 teriorly eccentric. It is closely related to D. ashleyi (Arnold), but 

 differs in its less eccentric apical system, less widely divergent posterior 

 petals, and thicker test. 



Geologic horizon. — Lower Etchegoin ( Jacalitos) and Upper Etche- 

 goin formations of the Pliocene. Associated with Astrodapsis arnoldi 

 peltoides (Anderson and Martin) in the Lower Etchegoin formation. 



Localities. — Holotype from "oil region of Tulare Lake," south of 

 Coalinga, Fresno County, California. Figured specimens from 

 Coalinga district. 



DENDRASTEE GIBBSII HUMILIS Kew, n. var. 

 Plate 25, figures 3a, 3b 



Echinarachniv^ excentricus var. Arnold. U. S. Geol. Surv. Bull., no. 322, 

 1907, pi. 24, fig. 8. 



Holotype.— i^o. 11379 Univ. Calif. Coll. Invert. Pal. 



This seems to be an intermediate form between Dendraster gibhsii 

 (Eemond) and D. ashleyi (Arnold), differing from the former in 

 liaving a thinner test with angailated margins ; from the latter it differs 

 in that the odd anterior petal is narrower, about the same width as 

 the anterior lateral pair, and in that the apical system is less eccentric. 



Geologic horizon. — Upper Etchegoin and Upper Fernando forma- 

 tions. Upper Pliocene; may be associated with Dendraster ashleyi. 



Localities. — Coalinga district, Fresno County, California, Univ. 

 Calif, loc. 2100 (holotype), and Santa Maria district, California. 



