no. 1617. NEW CRETACEOUS AND TERTIARY FOSSILS—ARNOLD. 359° 
HOCENE SPECIBS. 
Ja GQleLUN| OID AN 
Genus CIDARIS Leske. 
CIDARIS MERRIAMI, new species. 
Plate XXXII, fig. 8. 
Description.—Spines subcircular in cross-section, as much as 4 mm. 
in diameter and probably over 40 mm. in length, tapering very 
slightly; surface sculptured by 13 or 14 prominent, narrow, nodose, 
ridge-like, longitudinal ribs separated by narrow, deeply incised 
grooves; the nodes are well defined, especially in the younger stages 
of growth, and are subelliptical in cross-section, their longer axis 
being parallel with the axis of the spine. Test unknown. 
Dimensions.—The longest fragment obtained was over 20 mm. in 
longitude, the maximum diameter 4.5 mm. 
Notes.—The test of this species 1s unknown, but the abundance and 
well marked characteristics of the fragments of the spines has been 
deemed of enough importance to justify a specific name. Seven 
specimens have been obtained at the type locality, each showing the 
characters described above. 
Named in honor of Dr. John Charles Merriam, ROMEO of pale- 
ontology at the University of California. 
Dr. Hubert Lyman Clark, who kindly examined the type and ounes 
specimens of C¢daris merriami new species, Cidaris branneri, new 
species, from the Oligocene (see p. 363), and C7daris species, a, from 
the middle Miocene (see p. 851), writes as follows concerning the rela- 
tionships of the various forms: 
The wax cast [Oidaris species, a] is a spine of a true Cidaris and very much 
like many spines of Some individuals of the species of Cidaris common on the 
west coast of Lower California, Mexico, and Central America, C. thouarsii. I 
do not think it shows a single feature by which it can be distinguished from 
thouarsti. If it is not thowarsii, it is certainly from the ancestor of that species. 
The other specimens [Cidaris merriami, new species] 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 
merriani, for it satisfies me that the species must have been allied to, if not 
identical with, Tretocidaris perplexa Clark (Cidarids, 1907, p. 205, pl. vi, figs. 
1-2; pl. vu, figs. 1-4), the only other living littoral Cidarid known from north 
of Panama (other, I mean, than thowarsii). So your material shows that the 
ancestors of both thouarsii and perplexa lived in the Tertiary, in California. 
T think the other spine [Cidaris branneri, new species], * * * which I said 
was like Goniocidaris, is almost surely a third species. 
Type.—Imperfect spine, Cat. No. 165488, U.S.N.M. 
Florizon.—Martinez formation, lower Eocene. 
Localities—Santa Cruz quadrangle, San Mateo County, locality 
No. 25, ridge between headwaters of San Lorenzo River and Pescadero 
Creek. (H.S. Gay, R. Arnold.) 
