OLIGOCENE ECHINODERMATA. 

 Class ECHINOIDEA. 

 Subclass REGULARIA ENDOBRANCHIATA. 

 Order CIDAROIDEA. 



Family CIDARID.E. 

 Genus CIDARIS Leske. 



Cibakis mortoni Conrad. 

 Plate LXXIII, figure 1. 



Cidaris mortoni Conrad, 1S50, Acad. Xat. Sci. Philadelphia Jour., 2d ser., vol. 2, p. 40, PL I, fig. 13. 



? Cidaris sp. Bouve, 1S51, Boston Soc. Nat. History Proc, vol. 4, p. 3. 



Cidaris mortoni Cotteau, 1S92, Paleontologie francaise, Echinides eocenes, p. 449. 



Cidaris mortoni, St.pf a.nin i, 1911, Soc. geol. italiana Boll., vol. 30, p. 698. 



Description. — The fragment of a Cidaris test, which is here figured and referred to Cidaris 

 ■mortoni, has all of the essential characteristics of the form figured and briefly described by 

 Conrad. The species is large, globose, and circular in ambital outline. The ambulacra are 

 straight, the pore openings round and somewhat distinct. The interambulacra are composed 

 of large plates, each bearing a large perforate and apparently uncrenulate tubercle. 



Localities. — Near Palmyra, Lee County, Ga. (type); Baker County, Ga. (figured specimen). 



Geologic horizon. — Yicksburg formation, lower Oligocene. 



Collection. — Boston Society of Natural History (1555). 



Cidaris smithi Clark, n. sp. 

 Plate LXXIII, figures 2a-c, 3. 



Determinative characters. — Test medium size, moderately tall, subcircular in ambital out- 

 line. Ambulacra narrow, slightly flexuous. Interambulacra broad, each with two rows of 

 primary tubercles perforate and crenulate, the areola surrounded by a row of secondary tuber- 

 cles. Miliary space small. 



Dimensions. — Diameter 35 millimeters; height 24 millimeters. 



Description. — The test of this species is of medium size, moderately tall, and subcircular 

 in ambital outline. 



The ambulacra are narrow, slightly flexuous, the poriferous zones separated by four rows 

 of granules at the ambitus, which become reduced to two rows both above and below. 



The interambulacra are wide, rather more than three times the width of the ambulacra. 

 Each plate bears a large primary tubercle which is perforate and crenulate and has a medium- 

 sized areola surrounded by a row of granules. The relatively narrow miliary space is thickly 

 covered with tubercles. 



A large tubercle was found with the test that probably belongs to the same species. Cer- 

 tain Cidaris spines found at the Central Salt Works, Clarke County, Ala., may represent the 

 same species. 



Locality. — The Rocks, Clarke County, Ala. 



Geologic horizon. — St. Stephens limestone (upper portion), lower Oligocene. 



Collection. — Alabama Geological Survey. 



39S00"— 15 11 157 



