1920] Kew: Cretaceous and Cenozoic Echinoidea 155 



Geologic horizon. — Wildcat series, Upper Pliocene. 

 Locality. — Holotype from near Cape Mendocino ; also occurs at 

 mouth of Bear River, Humboldt County, California. 



Genus SPATANGUS Lamarck 



SPATANGUS PACHECOENSIS Pack 

 Plate 42, figures 4a, 46, 4c, id 



Spatangus pacliecoensis Pack. Univ. Calif. Publ. Bull. Dept. GeoL, 



vol. 5, 1909, p. 276, pi. 23, figs. 4, 5. 

 Spatangus {?) pacliecoensis. Lambert, Eev. C'rit. paleozoologie, vol. 4, 



1910, p. 55. 



Spatangus (?) pacliecoensis. Stefanini, Boll. Soe. geol. ital., vol. 30, 1911, 

 p. 705. 



Spatangus ? pachecoensis. Clark and Twitchell, U. S. Geol. Surv. Mon., 

 vol. 54, 1915, p. 156. 



Cotypcs. — Nos. 11330 and 11331; topoiype, specimen no. 11020 

 Univ. Calif. Coll. Invert. Pal. 



Test small. Measurements of specimen no. 11020 : anteroposterior 

 diameter 23.7 mm., transverse diameter 25.6 mm., greatest height 

 10.6 mm. Marginal outline subcordate, slightly truncated in the odd 

 posterior interambulacrum, and deeply notched in the anterior am- 

 bulacral area. Apical system eccentric anteriorly. Upper surface 

 broadly convex to the apex, which is situated about half way between 

 the apical system and the posterior margin ; somewhat flattened on 

 top. Petals of the bivium broad and elliptical in outline ; rows of 

 pores converge but little at their extremities. Anterior lateral petals 

 slightly narrower and shorter than those of the bivium ; angle between 

 the former nearly 180 degrees, distal ends curved forward. Posterior 

 rows of pores regularly curved ; anterior rows diverge from the pos- 

 terior rows markedly at first, then continue in almost straight lines to 

 the distal ends of the petals, where they finally curve forward. Odd 

 anterior petal short, wide, and placed in a broad, shallow sulcus which 

 becomes deeper at the margin, passes through a marginal notch, and 

 continues on the under side to the peristome. Inferior surface some- 

 what concave near the mouth. Episternum raised and produced pos- 

 teriorly to form a broad keel. Peristome eccentric anteriorly, large, 

 semicircular in outline, and with prominent posterior labrum. Peri- 

 proct large, round, and placed high up on the posterior truncation of 



