60 



University of California Puhlicatiom in Geology [Vol. 12 



outer row, the inner row being situated on the slope of the raised 

 area of the petal. Pores conjugate. Actinal surface deeply sunken 

 to the peristome. Ambulacral furrows broad, deep, and extending 

 undivided to the edge of the test. Anus inframarginal. Tubercles 

 small and of uniform size on both actinal and abactinal surfaces. 



Related forms. — This species is not related to any living form in 

 the Gulf of California. It resembles slightly Scutella gahbi (Remond) 

 from the San Pablo formation of middle California. The shape of 

 Clypeaster carrizoensis is more nearly pentagonal, the edges of the 

 test thicker, and the apical system more nearly central than in Scutella 

 gahhi. 



Geologic horizon. — Lower Division of the Carrizo Creek beds. 

 Pliocene. 



Locality. — Coyote Mountain, Imperial County, California. Holo- 

 type from Univ. Calif, loc. 738. 



CLYPEASTER DESERTI Kew 

 Plate 7, figures la, lb 



Clypeaster deserti Kew. Univ. Calif. Publ. Bull. Dept. Geol., vol. 8, 1915, 

 p. 48, pi. .3. 



Holotype.—'No. 10056 Univ. Calif. Coll. Invert. Pal. 



Test large. Average measurements : anteroposterior diameter 80.3 

 mm., transverse diameter 78 mm., greatest thickness 10.6 mm. Pen- 

 tagonal to subcircular in outline. Margins broadly notched opposite 

 the interambulacral areas, the two lateral posterior notches being 

 larger and the median i^osterior notch smaller than the anterior ones. 

 Test not markedly thick, but margin swollen except opposite the 

 posterior intei-ambulaeral area. Apical system central and raised. 

 Petals short, very tumid, reaching about half the distance to the edge 

 of the test and tending to close at their ends, those of the trivium 

 to a greater degree than those of the bivium. Anterior petal longer 

 than the other four, which are of approximately the same length. 

 Poriferous areas broad, and pores conjugate. Tubercles small and 

 of the same size on both sides. Actinal surface flat, with mouth 

 central and slightly sunken. Anus large and inframarginal. Internal 

 structure made up of concentric rows of slender pillars near the edge 

 of the test. 



Related forms.— -This species may be distinguished from the Recent 

 Clypeaster rotundus A. Agassiz of the Gulf of California, by its more 



