PLEISTOCENE ECHINODEBMATA. 225 



two strong furrows which diverge for a short distance then converge slightly and continue 

 nearly to the margin, giving off one large and many small branches on the way. Near the 

 margin the large furrows split up into many small ones which o:i well-preserved fossil specimens 

 and in recent specimens can be seen to continue over the margin and on the upper surface for a 

 considerable distance. 



The periproct is very small, usually circular, but sometimes subelliptical by longitudinal 

 elongation; situated from 1 to 10 millimeters from the posterior border, being more distant in 

 the large specimens. 



Related forms. — D. excentricus is closely related to both D. coalingaensis and D. gibbsii. 



D. coalingaensis differs in being smaller, more uniformly depressed and therefore less tumid 

 centrally, in having its apex more excentric posteriorly and more nearly coincident with the apical 

 system and its periproct usually nearer the margin. The features in which I). coalingaensis 

 resembles D. excentricus are so fundamental as to suggest that it is probably an ancestral form. 

 D. gibbsii differs from D. excentricus in having its apex and apical system much more excentric 

 posteriorly, its posterior ambulacra! petals more widely divergent and with poriferous zones 

 also diverging more widely from each other as well as differing more in length and its periproct 

 usually nearer the posterior border. There do not appear to be any foreign forms closely related 

 to the present species. 



Localities. — San Diego -(figured specimen A) ; Ventura County (figured specimen B) ; San 

 Luis Obispo (Conrad's type); Riverside County; San Pedro (Cooper, Arnold), Santa Barbara 

 (Gabb, Arnold) ; Seven Mile Beach, San Mateo County (Cooper) ; San Fernando, Los Angeles 

 County (Cooper); all in California. 



Geologic horizon. — San Pedro formation, Pleistocene. 



Collections. — Wagner Free Institute of Science (2473, A); U. S. National Museum; Yale 

 University; California Academy of Natural Sciences; Johns Hopkins University (T 2, B). 



Genus MELLITA Agassiz. 



Mellita pentapora (Gmelin). 



Plate CVI, figure 1; Plate CVII, figures la-c. 



Echinus pentaporus Gmelin, 1788, Linne, Systema naturae, vol. 1, pt. 6, p. 3189. 



Mellita testudinata Klein, 1734, Nat. disp. Echinoderniata, p. 25, PL XXI, fig. C, D. (Copied in Enc. M., PI. CXLIX, 



figs. 3, 4.) 

 Scutella quinquefora Lamarck, 1816, Animaux sans vertebres, p. 9. 

 Scutella quinquefora Lamarck, 1840, Animaux sans vertebres, 2d ed., p. 280. 



Mellita testudinata Agassiz, 1841, Mon. echinodernies vivans et fossiles, Des scutelles, p. 40, PL IV, figs. 7-9. 

 Mellita quinquefora Agassiz, 1841, Mon. echinodermes vivans et fossiles, Des scutelles, p. 36, PL III. 

 Mellita ampla Holmes, 1847? MS. 



Mellita ampla Ravenel, 1848, Echinidae, recent and fossil, South Carolina, p. 2. 

 Mellita ampla Tuorney, 1848, Rept. Geology South Carolina, p. 205. 

 Mellita ampla Ravenel, 1850, Am. Assoc. Adv. Sci. Proc, vol. 3, p. 160. 

 Mellita ampla Michelin, 1S55, Soc. geol. France Bull., 2d ser., vol. 12, p. 759. 

 Mellita texana Conrad, 1856, Acad. Nat. Sci. Philadelphia Proc, vol. 8, p. 316. 

 Mellita testudinata Desor, 1858, Synopsis des echinodermes fossiles, p. 237. 

 Mellita ampla Michelin, 1858, Rev. et mag. zool., 2d ser., vol. 10, pp. 362, 363, PL IX, fig. 1. 

 Mellita quinquefora var. ampla Holmes, 1860, Post-Pliocene fossils South Carolina, pp. 3, 4, PL I, fig. 6. 

 Mellita ampla, Dujardin and Hupe, 1862, Hist. nat. zoophytes echinodermes, p. 567'. 

 Mellita pentapora Liitken, 1S64, Bid. til Kunds. om Echinodermes, VidenSk. Medd. Kj0benhavn. 

 Mellita texana Meek, 1864, Smithsonian Misc. Coll., vol. 7 (183), p. 2. 

 Mellita testudinata Agassiz, 1872, Revision of the Echini, pp. 141, 142. 



Mellita testudinata Hilgard and Hopkins, 1878, Rept. Com. Engineers of Jan. 1875; suppl., pp. 23-33, 49, PL III, fig. 12. 

 Mellita pentapora Clark, 1902, U. S. Fish Com. Bull., p. 565, PL X. 

 Mellita ampla Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 708. 



Determinative characters. — Test medium to very large; subpentagonal in marginal outline, 

 broadest opposite anterior paired petals; five long narrow lunules equal or subequal in length; 

 margin thin, with a shallow notch at the anterior end ; the whole form much depressed, the upper 



