56 University of California Publications in Geology [Vol. 12 



The description of the test is taken from an imperfect young 

 specimen. 



Geologic horizon. — Lower Division of Carrizo Creek beds, Pliocene. 

 Locality. — Coyote Mountain, Imperial County, California, Univ. 

 Calif, loc. 738. 



Order CENTRECHINOIDA Jackson 

 Suborder CAMARODONTA Jackson 



Family ECHINIDAE Agassiz 

 Genus TRIPNEUSTES Agassiz 

 TEIPNEUSTES (HIPPONOe) OALIFORNICUS (Kew) 

 Plate 3, figure 5 



Hipponoe caJifornica Kew. Univ. Calif. Publ. Bull. Dept. Geol., vol. 8, 



1914, pp. 50-51, pi. 1, fig. 2. 

 Hipponoe calif ornica. Clark and Twitehell, U. S. Geol. Surv. Mon., vol. 



54, 1915, p. 111. 



Holotypr.—No. 10055 Univ. Calif. Coll. Invert. Pal. 



Size of test large. Measurements of specimen no. 10055 : trans- 

 verse diameter approximately 85 mm., greatest thickness approxi- 

 mately 75 mm. Thin and conical in shape, with the ambitus situated 

 near the base. Actinal surface somewhat concave. Ambulacra broad, 

 with the poriferous area equal to the non-poriferous area. Poriferous 

 zones consisting of three pairs of conjugate pores arranged obliquely 

 and placed one above the other, forming radial lines. Middle pair 

 sporadic. Furrows joining pores become very marked below ambitus. 

 Tubercles on ambulacra irregularly placed on both poriferous and 

 non-poriferous plates. Interambulacral area twice as wide as the 

 ambulacral area. Five primary tubercles on each interambulacral 

 plate near the ambitus and arranged in radial rows. The number of 

 tubercles becomes less toward the apical system. 



Related forms. — The Recent Hipponoe depressa A. Agassiz found 

 in the Gulf of California and on the west coast of Lower California 

 is closely allied to Tripneustes californicus. The latter has fewer 

 tubercles than the former ; also the ambitus is situated lower down, 

 giving it a more distinctly conical shape. 



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

 Pliocene. 



Locality. — Coyote Mountain, Imperial County, California, Univ. 

 Calif, loc. 2064. 



