128 MESOZOIC AND CENOZOIC ECHINODEEMATA OF THE UNITED STATES. 



Genus MORTONELLA Pomel. 

 non Mortonia Gray, 1851. 



Mortonia Desor, 1857, Synopsis des echinides fossiles, p. 231. 



Mortonella Pomel, 18S3, Classif. niethodique et genera des echinides vivants et fossiles, p. 70. 

 Mortonella Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 684. 



The genus Mortonella as used here includes the scutella-like forms having a central or sub- 

 central apical system, periproct less than halfway from peristome to margin, thick margin, five 

 genital pores, and ambulacral area either flat or tumid. The general form is discoidal. The 

 ambulacral furrows are simple and straight for halfway to the margin, then bifurcate and proceed 

 to the margin without much further branching. The ambulacral petals extend slightly more 

 than halfway to the margin and are open at the ends. The chief difference between Mortonella 

 and Periarchus is in the thickness of the margin. 



Mortonella quinquefaria (Say). 

 Plate LX, figures 2a-2f; Plate LXI, figures la-b. 



Scutella quinquefaria Say, 1S25, Acad. Nat. Sci. Philadelphia Jour., 1st ser., vol. 5, p. 228, no fig. 



non Scutella rogersi Morton, 1834, Synopsis organic remains Cretaceous, p. 77, PI. XIII, fig. 3. 



non Scutella rogersi Desmoulins, 1837, Etudes sur les echinides, Tabl. synon., p. 236. 



non Lagana rogersi Agassiz, 1S40, Cat. syst. ectyporum echinodermatum fossilium musei Neocomensis, p. 6. Merely 

 listed Morton's form. 



Scutella rogersi Agassiz, 1841, Mon. echinodermes vivans et fossiles, vol. 2, Des scutelles, pp. 85, 86, PL XIX, 

 figs. 1-4. Described and figured Say's form under the impression that he was dealing with Morton's. 



Scutella rogersi Agassiz (pars), 1847, Cat. raisonne echinodermes, vol. 7, p. 135. 



Scutella rogersi Bronn (pars), 1848, Index palteontologicus, vol. 1, p. 1126; vol. 2, p. 196. 



Mortonia rogersi Desor (pars), 1858, Synopsis des echinides fossiles, p. 231, no fig. Described Say's form but cited Mor- 

 ton's figure. 



Mortonia rogersi Dujardin and Hupe, 1862, Hist. nat. des zoophytes echinodermes, p. 563. 



Mortonia rogersi Conrad (pars), 1865, Acad. Nat. Sci. Philadelphia Proa, p. 74. 



Mortonia quinquefaria (Say) Conrad, 1866, Smithsonian Misc. Coll., vol. 7 (200), p. 32. 



Scutella rogersi Quenstedt, 1872-1875, Petrefact. Deutschlands, pt. 1, vol. 1, Echiniden, pp. 525, 546. 



Mortonia rogersi Zittel, 1876-1880, Handbuch der palaeontologie, vol. 1, pt. 1, p. 522. 



Mortonia rogersi Agassiz, 1883, Mus. Comp. Zoology Mem., vol. 10, No. 1, p. 88. 



Mortonella rogersi Pomel, 1883, Classif. meth. et genera des echinides vivants et fossiles, Alger., p. 70. 



Scutella mortoni (Agassiz) Quenstedt, 1885, Handbuch der Petrefactenkunde, p. 696. 



Scutella (Mortonia) rogersi De Gregorio (pars), 1890, Mon. faune eocenique Alabama, p. 250, PL XLII1, figs. 16-20. 



Mortonia quinquefaria Gregory, 1891 (discussion), Geol. Soc. America Bull., vol. 3, p. 105. 



Echinanthus quinquefaria Gregory, 1891 (tabulation), Geol. Soc. America Bull., vol. 3, p. 105. This was evidently a 

 lapsus calami. 



Scutella rogersi Boyle, 1893, U. S. Geol. Survey Bull. 102, p. 263. 



non Mortonia rogersi Dana, 1895, Manual of geology, 4th ed., p. 898, fig. 1491. 



Mortonella rogersi Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 685. 



Determinative characters. — Test of medium size; discoidal; circular to broadly subovate in 

 marginal outline; much depressed, upper surface more or less tumid centrally, margin and sub- 

 marginal area thick; under surface flat. Ambulacral petals large, broad, spatulate, extending 

 nearly two-thirds of the distance to the margin. Apex and apical system subcentral. Peri- 

 stome small, circular; ambulacral furrows simple and straight nearly halfway to the margin, 

 then forking symmetrically. Periproct very small, circular, about half the distance from peri- 

 stome to posterior margin. 



Dimensions. — Specimen A: Length 56 milhmeters; width 58 nullimeters; height 14 milli- 

 meters. Specimen B: Length 59 miUimeters; width 61 milUmeters; height 8 milhmeters. 



Description. — This species was one of the earliest Cenozoic forms reported from American 

 deposits. It was first described by Thomas Say in 1825. Two specimens, which are probably 

 Say's types, were found by the writer in the collection of the Academy of Natural Sciences of 

 Philadelphia. This species has been often confused with Clypeaster rogersi (Morton) , owing partly 

 to a superficial resemblance, but more to the mistakes of L. Agassiz and Desor. Agassiz was the 

 first to figure Say's form; but unfortunately having figured and described what was in reality 



