1920] Kew: Cretaceous and Cenozoic Echinoidea 135 



Geologic horizon. — Lower Merced formation, Wildcat series, and 

 Purisima formation. Upper Pliocene. 



Localities. — Cotypes from Eel Eiver, Humboldt County, Califor- 

 nia. Univ. Calif. Iocs. 71 and 1876. 



Genus SCUTASTER Pack 



SCUTASTER ANDEESONI Pack 

 Plate 26, figures 3a, 36 



Scutasier andersoni Pack. Univ. Calif. Publ. Bull. Dept. Geol., vol. 5, 1909, 



pp. 278-279, pi. 23. 

 Scutaster andersoni Pack. Ihid., vol. 7, 1913, pp. 301-302, pi. 15, figs. 



2a, 2b. 



Scutaster andersoni. Stefanini, Boll. Soc. geol. ital., vol. 30, p. TO-i. 

 Scutaster andersoni. Clark and Twitchell, U. S. Geol. Surv. Mon., vol. 54, 

 1915, p. 206, pi. 93, fig. 1. 



Holotype.— No. 11029 Univ. Calif. Coll. Invert. Pal.; lectotijpe, 

 in U. S. Nat. Mus. 



Pack's original description is as follows: 



Bimensions. — Diameter through the anterior petal 53 mm. ; diameter between 

 the lateral margins 62 mm., height 5 to 6 mm. 



Test subeircular in outline, eilges markedly thin. Upper surface regularly 

 arched from the margin ; apex anterior to the center. Apical system small and 

 apparently central. Ambulacral star small; petals extending slightly less than 

 half way to the margin of the test, closed at the ends. Lateral petals broader 

 than the posterior ones, but of almost the same length. Poriferous zones broad, 

 and continuing full width almost to the ends of the petals. In the posterior 

 petals the interporiferous area forms aVjout one-third the width of the petal. 

 Poriferous zones of the lateral petals equal in width to those of the posterior 

 petals, but enclosed area broader. In the extension of the three anterior petals 

 are broad lunules, over half as long as the petals ; shallow grooves extend from 

 the lunules to the margin. Anterior lunule slightly farther from the apical 

 system than are the lateral ones. Prom the ends of the posterior petals the 

 plates enlarge, and the area broadens rapidly. No lunules were seen here, nor 

 in the posterior interanibulacral space. They may be represented by marginal 

 notches, as the posterior edge of the specimen is lacking. 



In the later description he says : 



The new material shows that the test is subeircular to oval in outline. The 

 apical system is slightly posterior to the middle of the test; the ratio of the 

 distance from the apical system to the posterior and anterior margins in the 

 figured specimen is as 23:30. The middle of the arch of the abactinal surface 

 is slightly anterior to the middle of the test, being located approximately in 

 the middle of the anterior petal. In the flgure<l specimen the distance from 

 the middle of the arch to tlie anterior margin is 21 mm., to the posterior margin 

 32 mm. The posterior ambulacra terminate rather abruptly, the edge of the 

 test forming broad, shallow notches which fashion the posterior interanibulacral 

 area into a process somewhat similar to that of Sculella norrisi. The test is 

 much compressed. In some cases there is a slight tendency for the arch of the 



