122 MESpZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



inconspicuous. Peristome central, unusually large, much larger than periproct, circular, with 

 crenulated margin. Periproct very small, nearer to posterior margin than to peristome. 



Dimensions. — Length 2 to 4 millimeters; width 1.5 to 3 millimeters; height 0.5 to 1 milli- 

 meter. 



Description. — This little echinoid occurs in comparative abundance in association with 

 Echinocyamus huxleyanus in the Gosport sand at Claiborne, Ala., and elsewhere. The test is 

 thin walled and fragile, very small, rarely reaching a quarter of an inch in length, discoidal in 

 general form, broadly oval to subcircular in marginal outline. The upper surface is very low, 

 rarely over a millimeter in height, flat or faintly convex; the sides rounded; the lower surface 

 nearly flat, or slightly concave. In a few specimens several faint radiating creases can be 

 distinguished on the lower side. 



The ambulacral petals are decidedly rudimentary, so inconspicuous as to be difficult to 

 discern on even good sjjecimens; short, extending less than halfway to the margin, the poriferous 

 zones nearly parallel and composed of very small pores in pairs which are not conjugated. 



The apical system is central or subcentral, usually broken out. The genital pores are very 

 small and can rarely be made out on the specimens. 



The whole surface of the test is covered with small tubercles, set in relatively large 

 scrobicules. 



The peristome is central and unusually large in proportion to the size of the test, its diameter 

 being 4 or 5 times that of the periproct. The periproct is very small, circular, and situated from 

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



Belated forms. — F. meridionalis is not closely related to any other American species. In its 

 fragility, size, and superficial characteristics it resembles E. huxleyanus, but differs in having a 

 more rudimentary apical system and ambulacral petals and in its very low, subcircular, discoidal 

 form. 



Localities. — Claiborne, Ala., and Jackson, Miss. 



Geologic horizon. — Gosport sand of Claiborne group, middle Eocene. 



Collections. — Johns Hopkins University (T 2005) ; U. S. National Museum. 



Family IAGANID.E. 



Genus LAGANUM BlainvUle. 



Laganum (?) crtjstuloides (Morton). 



Plate L VII, figures 5a-d, 6a-d. 



Seutella crustuloides Morton, 1833, Am. Jour. Sci., 1st ser., vol. 24, p. 131, PI. X, fig. 8. 



Scutella crustuhides Morton, 1834, Synopsis Organic Remains Cretaceous, p. 77, PI. XV, fig. 10. 



Seutella crustuloides Morton, 1842, Acad. Nat. Sci.. Philadelphia Jour., 1st ser., vol. 8, p. 217. 



Scutella crustuloides Bronn, 1848, Index Palseontologicus, vol. 1, p. 1126; vol. 2, p. 196. 



Scutella crustuloides Ravenel, 1848, Echinidse, recent and fossil, of South Carolina, p. 2. 



Scutella crustuloides Ravenel, 1S50, Am. Assoc. Adv. Sci. Proc, vol. 3, p. 160. 



Sismondia crustuloides Desor, 1858, Synopsis des echinides, p. 227. 



Scutella crustuloides Gabb, 1859, Cat. Invert. Fossils Cretaceous, p. 19. 



Scutella crustuloides Dujardin and Hupe, 1862, Histoire nat. zoophytes echinodermes, p. 559. 



Sismondia crustuloides Conrad, 1865, Acad. Nat. Sci. Philadelphia Proc, pp. 74-75. 



Sismondia crustuloides Conrad, 1S66, Smithsonian Misc. Coll., vol. 7 (200), p. 21. 



Scutella crustuloides De Gregorio, 1890, Mon. faune eocenique Alabama, p. 251, PL XLIII, figs. 24^25 (reprod. from 



Morton). 

 Sismondia crustuloides Cotteau, 1891, Paleontologie francaise, Echinides eocenes, vol. 2, p. 300. 

 Scutella crustuloides Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 77. 

 Scutella crustuloides Boyle, 1893, U. S. Geol. Survey Bull. 102, p. 262. 

 Periarchus (?) crustuloides Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 699, 



Determinative characters. — Test small, subpentagonal, suboval or subovate in marginal out- 

 line. Upper surface low, tumid centrally; margin very thick, submarginal area flat or nearly so, 

 about the same thickness as the margin. Lower surface concave. Apex and apical system 

 slightly excentric anteriorly. Ambulacral petals lanceolate, pointed and closed at the ends, 



