204 MESOZOIC AND CENOZOIC ECHINODEEMATA OF THE UNITED STATES. 



being deeper, narrower, and more pronounced than the rest. The ridges are all conspicuous, 

 but the odd anterior one is the highest and most pronounced, constituting the anteriorly excen- 

 tric apex of the test. The details of the under surface could not be made out on the specimen. 



The ambulacral areas are wide, slightly wider than the interambulacral areas at the mar- 

 gin; dorsal portions subpetaloid. The inner parts of the peatals are tumid and elevated, 

 the outer parts depressed. The inner rows of pores gradually and continuously diverge to about 

 one-fourth inch from the margin. The outer rows first diverge and then converge around the 

 tumid parts of the petals and approach near to the inner row, beyond which point both rows 

 diverge slightly to the margin. The inner rows of pores are large and round, the outer rows 

 oval. There are one or two extra rows of pores within the main inner row. The pairs of pores 

 are conjugated. 



The apical system is excentric anteriorly, decidedly depressed below the surface of the 

 petals. The details could not be made out. 



The under surface not being exposed the details in regard to the peristome and ambulacral 

 grooves can not be given. The periproct is small, inframarginal, almost marginal. 



Related forms. — A. jacaUtosensis is most closely related to A. arnoldi, which differs in 

 having a less depressed apical region and not having the interambulacral depressions continu- 

 ing to and joining the apical depression; also in having the inner rows of pores of each petal 

 nearly parallel. 



Locality. — -South of Garza Creek, a mile southeast of Clark's place, Coalinga district, Cal. 



Geologic horizon. — -Jacalitos formation, upper Miocene. 



Collection.— XI . S. National Museum (165G10). 



Genus MELLITA Agassiz. 



Mellita caboliniana Kavenel. 



Plate XCI, figures la-b; Plate XCII, figures la-b. 



Scutella caroliniana Kavenel, 1841, Acad. Nat. Sci. Philadelphia Jour., 1st ser., vol. 8, pp. 333, 334, text figure. 



non Mellita hexapora L. Agassiz, 1841, Mon. echmodermes vivans et fossiles; Des seutelles, p. 41, PI. IV, figs. 11, 12. 



Mellita caroliniana Ravenel, 1S48, Eehinidae, recent and fossil, of South Carolina, p. 160. 



Scutella carolinensis Tuomey, 1848, Geology South Carolina Kept., p. 208. 



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



Mellita caroliniana Tuomey and Holmes, 1S55, Pliocene fossils South Carolina, pp. 3, 4, PL I, fig. 4. 



non Mellita hexapora Desor, 1858, Synopsis des echinides fossiles, p. 237. 



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



Mellita caroliniana Conrad, 1865, Acad. Nat. Sci. Philadelphia Proc, p. 74. 



Mortonia (Pcriarchus) carolinensis Conrad, 1866, Smithsonian Misc. Coll., vol. 7 (200), p. 21. 



non Mellita sexforis, A. Agassiz, 1S72, Revision of the Echini, pp. 141, 320. 



non Mellita sexforis Gregory, 1891, Geol. Soc. America Bull., vol. 3, p. 107. 



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



Periarchus carolinensis ? Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 699. 



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



Determinative characters. — Test small to very large; subcircular to subpentagonal in mar- 

 ginal outline, broadest between the anterior and posterior pairs of petals; six lunules, the odd 

 posterior one much longer than the posterior pair which are longer than the rest ; margin thin ; 

 the whole form greatly depressed, the upper surface rising gradually and but slightly from the 

 margin to the very low, subcentral or posteriorly excentric apex; under surface flat. Ambu- 

 lacral petals large, the posterior pair longer than the others. Apical system excentric ante- 

 riorly. Peristome small, subcircular, excentric anteriorly; ambulacral furrows simple and 

 straight near the peristome, then forking, each pair of branches diverging and again converging 

 near the margin. Periproct very small, elliptical, between the inner end of the odd posterior 

 lunule and the peristome. 



Dimensions. — The large form figured gave: Length 159 millimeters; width 152 millimeters; 

 height about 10 millimeters. 



