126 MESOZOIC AND CENOZOIC ECHINODEKMATA OF THE UNITED STATES. 



straight for about half the distance to the margin. Periproct very small, subcircular, about 

 one-fourth the way from the posterior margin to the peristome. 



Dimensions. — Length 40.5 millimeters; width 39 millimeters; height 5 millimeters. 



Description. — This new species is rare, only a single specimen having yet been discovered. 

 As this specimen was found in South Carolina, the form is named in honor of that distinguished 

 worker upon the geology and paleontology of South Carolina, Mr. M. Tuomey. The test is 

 medium in size. In marginal outline it is subovate, broadest posteriorly, narrowing until some- 

 what pointed anteriorly, truncated along the middle of the posterior border. The whole form is 

 greatly depressed, being quite flat all around the area outside the ambulacral petals, and within 

 the petaloidal area rising only slightly to form a very low broad mound. The margin of the test 

 is thin, with two shallow notches opposite the ends of the posterior petals. The flattened mar- 

 ginal area, from the ends of the petals to the edge, is thin and rather narrow, especially ante- 

 riorly, where it is decidedly less wide than the petals are long, while posteriorly the width is 

 about equal to the length of the petals. The under surface is flat or slightly concave from 

 edge to edge. The apex is central or subcentral, at the summit of the tumid area. 



The ambulacral areas are narrow in the petaloid region, but wide at the margin, where they 

 are wider than the mterambulacral areas. The dorsal portions are petaloid. The petals are 

 of medium size, subequal in length, narrowly elliptical in form, slightly open at the ends; the 

 posterior pair extending about half, the others decidedly more than half, the way to the margin. 

 The poriferous zones are rather wide, almost as wide as the interporiferous areas; inner row of 

 pores oval, the outer slitlike; the pairs of pores conjugated. A few pairs of pores extend beyond 

 the ends of the petals. 



The mterambulacral areas are rather wide between the petals, wider than the ambulacral 

 areas; of nearty uniform width to the margin where somewhat narrower than the ambulacral 

 areas; composed of large polygonal plates. The whole surface of the test is covered with small 

 uniform tubercles, which are slightly larger on the under side. 



The apical system is central or subcentral; coincident with the apex. The details are 

 indistinct upon the specimen; but the madreporite is relatively large, flush with the surface, 

 with five genital pores near its edge. 



The peristome is small, circular or subcircular, subcentral; the ambulacral furrows appar- 

 ently simple and straight for about half the distance to the margin, where, they probably fork 

 symmetrically though they do not show well on the only specimen found. 



The periproct is very small, about half the diameter of the peristome, subcircular, approach- 

 ing an inframarginal position, being situated on the under surface about one-fourth the way from 

 the posterior margin to the peristome. 



Related forms. — -This species is very similar to some specimens of Periarchus lyelli, but differs 

 from it in being more pointed anteriorly, in being truncated posteriorly, and in having its 

 periproct nearer to its posterior border. S. conradi resembles S. tuomeyi, but can be separated 

 by its smaller size, subquadrate posterior end, emarginate posterior border, and nearer approach 

 of periproct to posterior border. S. tuomeyi also resembles S. mississippiensis in general 

 appearance, but the latter is readily distinguished by the submargmal location of its periproct. 

 There do not appear to be any foreign forms which are closely related. 



Locality. — Fourteen miles south of Fort Motte station, Orangeburg County, S. C. 



Geologic horizon. — Eocene, probably from the McBean formation of the Claiborne group, 

 middle Eocene. The specimen occurred in a greensand matrix. 



Collection.— U. S. National Museum (137970). 



SCUTELLA (?) CONRADI (Cotteail). 



Plate LXIV, figures la-d. 



non Scutella marginalia Desmoulins, 1837, Etudes sur les echinides, Tabl. synon., p. 234. 

 non Laganum marginale, Agassiz and Desor, 1847, Cat. raisonn6 echinodermes, vol. 7, p. 133. 

 non Sismondia marginalia Desor, 1858, Synopsis des echinides, p. 226, PI. XXVII, figs. 26-28. 

 Sismondia marginalis Conrad, 1865, Acad. Nat. Sci. Philadelphia Proa, p. 75, no fig. 

 Mortonia (Periarchus) marginalis Conrad, 1866, Smithsonian Misc. Coll vol. 7 (200), p. 21. 



