52 ^ University of California Publications in Geology [Vol. 12 



Class ECHINOIDEA Bronn 

 Order CIDAROIDA Duncan 



Family CIDARIDAE Gray 

 Genus CIDARIS Leske 



CIDARIS LOEENZANUS (Arnold) 

 Plate 3, fignre 4 



Cidaris branneri Arnold. Proc. U. S. Nat. Mus., vol. 29, 1903, pp. 363, 

 364, pi. 33, fig. 5. 



Cidaris branneri. Stefanini, Boll. Soe. geol. ital., vol. 30, 1911, p. 698. 

 Cidaris branneri. Clark and Twitchell, U. S. Geol. Surv. Mon., vol. 54, 

 1915, p. 158, pi. 73, fig. 5. 



Holotijpe.—No. 1056, U. S. Nat. Mus. 



Arnold 's description will be given, since no specimen of this species 

 has been examined : 



Test unknown. Spines, long, slender, circular in cross section, attaining a 

 length of at least 25 millimeters and a diameter of over 2 millimeters. Surface 

 of sjjine smooth for about one-fifth its length from the base; above this it is 

 ornamented by ten longitudinal rows of elongated nodes or granules which are 

 barely connected near the smooth portion, but which partake more and more of 

 the character of nodose ribs toward the distal end; the last one-fifth of the 

 spine is ornamented by five prominent, slightly nodose ribs; the extreme end is 

 blunt and rounded; collar at base only faintly developed. 



The spines of this species are easily distinguishable from those of C. merriami, 

 new species, from the Eocene, by their smaller size, fewer but much more promi- 

 nently nodose longitudinal ribs, and smooth basal portion. No complete spine 

 of C. merriami was obtained, so that the smooth basal section may possibly be 

 a characteristic of this latter species as well as C. lorenzanus. 



According to Twitchell, the dimensions are : 



Length 20 millimeters; diameter, basal end 2.2 millimeters, distal end 1.1 

 millimeters. 



The name Cidaris tranneri has been previously used by White^ 

 for a species occurring in Brazil. This has necessitated the change 

 to C. lorenzanus (Arnold). 



Geologic horizon. — San Lorenzo formation, Oligocene. 



1 White C. A., Contributions to the paleontology of Brazil, Museo nac. Rio de 

 Janeiro Archivos, vol. 7, pp. 247-248, pi. 28, figs. 2, 3, 1888. 



