1920] Kew: Cretaceous and Cenozoic Echinoidea 



129 



coalingaensis Twitchell, which it resembles very closely, it differs in 

 having a less eccentric apical system and small interambulacral 

 grooves. 



Geologic horizon. — San Diego formation, Upper Pliocene. 

 Localities. — Cedros Island, Lower California; Pacific Beach, San 

 Diego County, California. 



DENDRASTER PERRINI (Weaver) 

 Plate 28, figures 3a, 3b, 3c 



Scutella perrini Weaver. Univ. Calif. Publ., Bull. Dept. Geol., vol. 5, 1908, 



p. 273, pi. 22, fig. 2. 

 Scutella perrini. Arnold, U. S. Geol. Surv. Bull., no. 396, 1909, pp. 30, 34, 



38, 162, pi. 28, figs. 1, 2. 

 Scutella perrini Arnold, U. S. Geol. Surv., Geol. Atlas, Santa Ci-uz folio 



(no. 163), p. 6. 



Astrodapsis perrini. Rathbun, Proo. U. S. Nat. Mus., vol. 3.5, 1908, p. 342. 



Listed on authority of R. Arnold and erroneously ascribed to Merriam. 

 EcMnodiscm (?) perrini. Lambert, Rev. crit. paleozoiilogie, vol. 13, 1909, 



p. 122. 



Scutella perrini. Arnold and Anderson, U. S. Geol. Surv. Bull., no. 398, 



1910, p. 338, pi. 50, figs. 1, 2. 

 Merriamaster perrini. Stefanini, Boll. Soc. geol. ital., vol. 30, 1911, p. 704. 

 Merriamaster perrini. Lambert, Rev. crit. paleozoologie, vol. 15, 1911. 



p. 64. 



Dcndraster perrini. Clark and Twitchell, U. S. Geol. Surv. Mon., vol. 54, 

 1915, pp. 190-191, pi. 88, figs. 2, 3a, 3b, 3c'. 



Holotype. — Specimen in Leiand Stanford Jr. Univ. Dept. Geol. ; 

 figured specimen, no. 11018 Univ. Calif. Coll. Invert Pal. 



Test rather small. Measurements of specimen no. 11038 Univ. 

 Calif. Coll. Invert. Pal. : anteroposterior diameter 43.8 mm., transverse 

 diameter 44.4 mm., greatest height 11.5 mm. Marginal outline sub- 

 circular to longitudinally suboval, with very faint notches in the 

 ambitus at the ambulacral areas; margin unusually thick, with the 

 upper surface greatly depressed but regularly arching to the summit, 

 which is subcenti'al. Apical system is posteriorly eccentric, being 

 about one-fifth to one-sixth the distance from the center to the margin. 

 Ambulacra wider than the interambulacra at the ambitus. Petals 

 large, broadly subellii^tical in outline, of unequal size, and liaving a 

 slight tendency to be elevated in all except in very young specimens ; 

 wide open at their extremities, and extending nearly to the margin. 

 Posterior pair of petals less divergent than the anterior pair ; ends 



