The fossil deposits provide support for the ecological conditions under which the tmna was able to survive. The hor1zo11 fran 1:1hioh the fossil ma'fJerial was obtained. lies on the Dorne-ine River, on the east flank of the Diabl·O Ranget: twelve miles north of Coalinga. The foasiliferoua beds of the Merychippus zone outcrop along this northern, southern coast and the type locality occurs on the.
The Mer:l'ohi;ppus zone was obtained from sandstones and conglomerates, two to three fe,et thick, lying on top of the middle. At this level, the material is usually concentrated in conglomerates and is most abundant at the top of the section. At least five hundred additional teeth were discarded for preservation .1 r fragmentar1. when kole.ncio.ns fro• tie.la. were :prepared in labari• . Tuesday7.
The last hundred fe.et or ae(1iment,a represents. the toreset portion of delta deposits. !he is rather 1mifo1,.m .st1-aa.t·i.fi:eation of the. The .chsirte, represents a compilation of data obtained from the writer's field observations and from references to publications by:.1erria.m, Heed, and. At the base of the type section is the fora.m1nife,ral zone characterized by Valvu : U.neria. aal.ifornica, one of the most widespread ant-faunal zones known in the.
Miocene age to this horizon and referred to · d. ist, 1mt- ly younger beds of Rioardo to tbe lcmer Pl.:loc.ene. In view of the late middle Miocene position of the Meryehippus zone, it may be possible that ·this material r·epre-. A narrow poeket w A poeket snall w However it is interesting to note that the relations of the form Coalinga.. seem to be vd.th t~ more :mem primitive• . bers of the J?roboscidea found in North America. Lack of group representatives in th1. s continent before middle Miocene time can tu.rm.ah a basis for regarding th& presen· e of these primitive :f.orms in Oali:fornia as an indication in . middle lvtiooen. age for the ·Merycbippus zone·. Horse remains are the clearest ant fossils found in the Mer;vehippus • area. indiv1du.al.s of this group eompris• . constituting approximately seven-three percent of the total population recorded from this horizon. Jor part of the oolleotion consists of isolated teeth referred to the species J~e;;y:chi;e;eus C!\l:ifQrnicus1 the type SJ)ecimen. JJ1U,s (Open) frotn the Maseall, Xn . A• ult~Jml.s the hypost7le eonsists of a single cusp,. while in the Ooalinga teeth th1s a.tl'Q.o tures are tr1engu.lar in shape and enclose a small tosaette.. other side, the upper third molars or .A:rohato•. bi11?J!UU ~om the lvieryohippus eone shows considerable reduction when compared with the two preceding molars. teeth the protocone and hypocones widen towards their base to an extent that significantly obstructs the opening of the. valley between protoloph and metaloph. the valley is wide open: n, and the two inland. None of the teeth of the lterychi:ppus zone ex•. hibtts tl• heav.v .internal oingul.um seen in the type of the Masea·11 specie.a.,. fhe '*eeth from t the Mer~bippus zone corresponds 1n almost all resl'>&ots with the· type and paratJPe of. Merriam) of -Barstow. !fhe onlJ' no1- ieeable di.tterenoe apel.'s to be the absence o:t an external cingul"Wn on the lowei' Jaw of the para:bJPe• !his · Character Taries consider• . abl7 1n the. large collection of teeth from the MerJCh1pl)u& area. and there seems to be no M.agnostic velttCh !'he goal material is referred to unquest1omb17· to. and teeth of the lower cheek the material must be connected in a pr ressive form pre- h.:tpp1ne has been shown by o · rosua, oe~nt abundant and proe. ;resive character of :ptyehoid orenulattona of metal walls:ph. serve in iBola.t.e form Ooa11nga from the type moat. walls ot· me~a.loph1 from the Mer7chippus area agree· alosel1 with P~ahl;e;a-u.'.s c:re~idt$ Scott orenidens~, 1n their less at:io:ngly developed ectoloph• forms of p:rH.$.o1oph, and hEHt'VY wear of - oeinent.ne, while ~imtlar 1n some: · characters, represent a ll\\\Oh larger horse. Compezieona with thts fo:m at'e inadequate , stnet does not m1lk hurt ot. h1U~I have been reeQgni;e: d in ooll.ectone from th«. some teeth in the collections of the Oalitornia Inst.it ute of Technolt>·Q by Jfais.oal1· and refer.e4 to .Parahiuus brevidt·ns Marsh are practical.o. teeth from Bo~th Ooa1!from.-. Oregon is northwestern Nevada., ~eth similar to. in Barstow and upper horizons of the !.Tiocene •. Merych1ppu.s oa11f o:rnieus Merriam. The teeth of me1%~1J?JlUS oal1fo.rnieus include almost 7 stops of all samples collected from this zone. tn.e· degree of variation of the eheek·tooth eba.raoters. aa se·n 1n this tool makes it difficult to decide. the e-JCe.ct. A general determination of the estimate. However, the braehler of the tooth tends to fight this tor with Aphelops rather than with it. The teeth show little development at the orochet and aa:tsecroehet. The two enamel pattern features were not associated in a single tooth. An a.teot1llne torm p~evious:cy- lm.ovm bJ a pair of teeth .. is shown in the oollectons b7 fifteen uppel:* and below .. mola:r!s and p111e.raolara1 Certain generio determina .t.: tons of the shape and. the basis is not true. but certain effects of the premolars are suggestive. These are also referred to this form. These SJ)ecimens are appropriate. To the writer's knowledge, no report has been published dealing directly with the geology of the San Joaquin Hills. The areal extent of the San Onofre facies in the Temblor is also greater than the map indicates. Except for the Ionic a.eposits of the Pleistocene terrace, all sediments are exposed. in the San Joaquin Hills may be attributed to the Miocene. The San Onofre faci~~ possesses approximately equal thickness on all sides of the area. Tilting of these deposits appears to be 'indicated, but not to the extent characteristic of the old deposits. Gentle curves in the fault trace indicate a slight dip of the fault plane to the west. The San Onofre Fau.lt enteJ~s the western end of the area dies h a vertical throw of perha.ps 1000 feet and. Ultësira Block and the area near the Lagoon south of the South Cross: b1ault Coastal Block. The trace of the Sliver fault appears to show a slight dip of the opening plane to the - northeast. Generally, all of these mistakes hit the wedge monkey mentioned above. The lowest known structural point is located southwest of the San Onofre fault and two miles northwest of Abalon Point. The area at the top of the wedge is roughly between the two up and down. The movement of the Bank Block relative to adjacent blocks cannot be precisely determined. A third possibility that is being carefully considered in the field considers the fault to be older than the deposition of the San Onofre. However, none of the older Miocene rocks cantri butecl to the San Ono.fre Breccia. Glaucophane occurs well down in the Temblor section and there are no similarities between the top of San Onofre and the oldest Miocene sediments. The relative earth motions causing the current uplift of the San Joaquin Hills have been investigated largely on a physiographic basis.Jeoimens re.present this spec1e· a