54 



University of California PiihUcatiom in Geology [Vol. 12 



H. L. Clark, who examined the specimens for Arnold, says: 



All appear to belong to one species, except possibly one fragment. That 

 piece might possibly have come from quite a different species. I am very glad 

 to see this material of merriiimi, for it satisfies me that the species must have 

 been allied to, if not identical with, Tetrocidaris perplexa Clark (Cidaridae, 

 p. 205, pi. 6, figs. 1, 2; pi. 7, figs. 1-4, 1907), the only other living littoral cidarid 

 known from north of Panama (other, I mean, than thouarsii) . So your material 

 shows that the ancestors of both thouarsii and perplexa lived in the Tertiary in 

 California. 



Geologic horizon. — Martinez group, Lower Eocene. 



Localities. — Holotype from Santa Cruz quadrangle, San Mateo 

 County, locality 25 ; ridge between head-waters of San Lorenzo River 

 and Pescadero Creek, California. Specimen, no. 11401 Univ. Calif. 

 Coll. Invert. Pal., from north side of Mount Diablo, Contra Costa 

 County, California. 



CIDAEIS TEHAMAENSIS Clark 

 Plate .3, figure 1 



Cidaris teJwrnaensis Clark. U. S. Geol. Surv. Mon., vol. 54, 1915, p. 44, 

 pi. 9, fig. 1. 



Holotype.— No. 31195 U. S. Nat. Mus. 



The writer has had no opportunity to study a specimen of this 

 species, and for this reason the description of Clark will be given 

 verbatim : 



This species is repjresented by a well-preserved spine that is large and club- 

 shaped. The granules are large and disposed in rows extending from the neck 

 to the point of the spine. 



Geologic horizon. — Knoxville formation. Lower Cretaceous. 

 Locality. — Shelton's ranch, Tehama County, California. 



CIDARIS THOUAESII(?) Valenciennes 



Cidaris thouarsii Valenciennes. Agassiz and Desor, Catalogue raisonne des 

 echinodermes, Ann. des sci. nat., vol. 6, 1846, p. 326. 



Cidaris sp. a Arnold. Proc. U. S. Nat. Mus., vol. 34, 1908, pp. 351, 359. 



Cidaris sp. a. Stefanini, Boll. Soc. geol. ital., vol. 30, 1911, p. 701. 



Cidaris thouarsii (.?)■ Clark and Twitchell, U. S. Geol. Surv. Mon., vol. 

 54, 1915, p. 179. 



Specimen in U. S. Nat. Mus. Coll. 



