EOCENE ECHINODEKMATA. 155 



Maceopneustes mortoni (Conrad). 

 Plate LXXII, figures la-d. 



Holaster mortoni Conrad, 1850, Acad. Nat. Sci. Philadelphia Jour., 2d ser., vol. 2, p. 40, PI. I, fig. 10. 

 Eohstcr mortoni Boyle, 1893, U. S. Geol. Survey Bull. 102, p. 150. 

 Macropneustcs mortoni Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 700. 



Determinative characters. — Test large, elevated, tumid, slightly cordiform, nearly round, 

 apex excentric forward. Ambulacra broad, petaloidal portions elongate, in very' shallow 

 depressions, nearly flush. Surface, of both ambulacral and interambulacral plates outside the 

 petals covered with numerous irregularly dispersed tubercles. Peristome forward about one- 

 third the distance from the anterior to the posterior margin. Periproct large, short distance 

 above margin. 



Dimensions. — Length 84 millimeters ; width S6 millimeters; height 52 millimeters. 



Description.— The test of the species is large, elevated, and tumid. It is slightly cordi- 

 form in ambital outline, nearly round but for the slight anterior groove and the ill-defined 

 posterior truncation. The apical system is excentric forward, the high upper surface giving 

 the test a somewhat subconical form. 



The ambulacra are broad, the petaloidal portions elongate, nearly flush in very shallow 

 depressions that reach far down the sloping sides. 



The petals of the ambulacra outside the petaloidal portions of the ambulacra and the 

 interambulacra are covered with numerous irregularly dispersed tubercles. 



The peristome is large, excentric forward, situated about one-third of the distance from 

 the anterior to the posterior margin. The periproct is large and situated a short distance 

 above the margin. 



Localities. — Palmyra, Lee County, Ga. (type); Fail, Choctaw County, Ala. (figured specimen) . 



Geologic horizon. — Jackson formation (upper Eocene) and Vicksburg formation (lower 

 Oligocene). 



Collection.— U. S. National Museum (14646S). 



Genus SARSELLA Pomel. 



Sarsella gregorti Clark, n. sp. 



Plate LXXII, figures 2a-d. 

 Sarsella sp. Gregory, 1892. 



Determinative characters. — 'Test small, cordiform, depressed. Apical system nearly cen- 

 tral. Ambulacra very diverse anterior in broad deep group, petaloidal portions of paired 

 ambulacra slightly sunken, the posterolateral more than the anterolateral. Several large, 

 irregularly dispersed tubercles crenulate and perforate on the interambulacra. Peristome 

 semilunar. Periproct high on posterior truncation. 



Dimensions. — Length 18.5 millimeters; width 17.5 millimeters; height 9 millimeters. 



Description.— This small form was noted by Gregory in his cursory examination of Ameri- 

 can echinoids when in America in 1891 and was referred to the genus Sarsella. The test is 

 small cordiform in ambital outline, depressed, only slightly higher on the posterior portion 

 of the upper surface than the anterior. The under surface is nearly flat. 



The ambulacra are very diverse. The anterior ambulacrum is situated in a broad deep 

 groove. The paired ambulacra have diverse slightly sunken petaloidal areas, the petals of the 

 posterolateral pair being broader and shorter and closed below while those of the anterolateral 

 pair are only imperfectly closed. 



The surface of the interambulacral plates bears a number of irregularly dispersed large 

 crenulate and perforate tubercles. They are confined to the paired interanibulacra. 



The apical system is small. The perforations in the four genitals are distinct on the type 

 specimen. 



