Kummel, 1954 Cephalopoda.Pdf

Bullettn of the Museurn of Compcrcrtive Zoologryt AT HARVARD COLLEGE Vol. 112, No. 3 Oc"ronnn,1954

Stottts of Inuertebrate Paleontology, lgSJ V. Mollusca: Cephalopoda Bv BpnNHAtsDKulrunr, Museum 6f Q6m,Farative Zoology, Cambriclge, Mass.

Few invertebrate classespossess (or are plagued with) the volume of literature and diversity of interpretation, or are so susceptible as media of philosophical speculation as the fossil cephalopods. A complete review of the literature and progress in the study of fossil cephalopodsis beyond the scope of this paper. Therefore I will center attention on the geologie distribution of fossil cephalopodsand current ideas on classification and evolution. The extent and degree of cooperation towards a uniformity of nomenelature- both morphological and taxonomic - that has prevailed in the past few years among the European and Ameri- can authors responsibiefor the Cephalopoda for the Treatise has been truly inspiring. The results of this labor will plaee the study of these animals on a new threshold. It is a pleasure to aclrnowledgethe data on Jurassic ammonoids furnished by w. J. Arkell; the data on Cretaceous ammonoids furnished by C. \Y. Wright; the data on Paleozoic ammonoids furnished by A. K. i\filler; the data on the Dibranchiata furnished by I_r.Bairstow; and data on nautiloid genera by Curt Teichert. of the three major groups of Cephalopoda,I will confine most of my remarks to the Ammonoidea. Recent tabulations in,ilicate that there are approximately 3000 valid genera of fossil cephalopodswith more than an additional thousand generic names which go into synonomy W-ithin the Nautiloiclea there are now recognized approximately 700 genera. Their evolutionary pattern is one of intense radiation in the ordovician during the initial phases of their evolution, follorved.by a rapid and steady decline until the present day with our one remaining relic genus. The main pattern of distribution of nautiloid genera as illustrated. on Figure t has been known for a long time. Morphologically the nautiloids are a highly diversified group but many of the orders that made their

I I82 BuTJIJETTN:MUSEUM ox' coMpARATIvEzoorJoGy appearaneein the Ordovician becameextinct by the Silurian and Devonian. During the latter half of the Paleozoicthe evolutionary rate of the nautiloids was greatly diminished. A second surge occurred in the llpper Triassic which has a diversified.nautiloid 2?5

NAUTILOID GENERA

Fig. 1. Bar graph showing number of nautiloicl genera in each geologio perioil. (Data from C. Teichert, personal communication.) '€pIIrlneNI lsolu uBc €prl€racolntl aqJ aql olur sarlrruBJOsaql Jo Sururo! aqf pue ?pl1erocorluaC aq+ Jo uorssa.rddnsaql s0181 -rssocauaFueqa srq;, '(gqOf 'laururny) pasodo.rddlsnor.tald se a€prlrlneu€red aql ueql raqler a€l]ilrln€uoFur"r.{gcISS€Iril al{l o} sprolrlneu crss€rrJ-lsod 1e Jo uoll€^rrap aql saFueqc a€pIIIlnBu -o8ur.rdg aql ol sorlrugJrer€alo su.o{s qop{,K (aepip1nu51.{guteg) 'suorsrlal salfr,t1dtsrB"arsserJJ .reddg ue Jo uorlruFoaal aqJ Jourlu .t1uo paau o1 .readde pue sdno"r8pauyap llalrr.se paldacce d11e.ra -ua8 a.re Bprleracoouo pue 'epr.rosocslg '€pl1€Jacoosy 'eprle.rac -ourlaqcrl\I'eprle"racopug'eprle.roooroursallfiat{l sroqlne osaql 'auop .dq pozruFoca.rsrapro eI aq] JO aq plnoqs slqt /vloq o? sB 'paanpa.r 1a,(se luauraa.r8eou lnq oq plnoqs lauirunx pu€ ra^4.old .{q pasodo.rd srapro Jo raqrunu aq} }Br{} slsrleroads prollln€u 'suralqo.rd Suoure luauraa.rFeaprl{. sr aJar{J IBoIlrJc aroru aql uo uorluol+B Furzrllelsf.rc ;o ?ca#aalq€rrsap .{.ra.taq} peq s€q ?r lnq pa,to.rdurraq .{lqeuorlsanbun ueo Fur>iurq1Surlsrxa SurzrJ€ruruns (OqOf) lauiurny pue ralrrold dq pasodo.rd,t11uacar airaqcs aarl 'ra}oereqa -€1u01ar{J a18urs€ uo paseq luauraFuerre cllerlralsds 'alq€ B Jo uorloafo.raql sI uor]Bcgrsselos(]]B{H Jo uor}cata.raq;, -ualun si auoqcs s,11ed11?Bql purru s,auofue ur lqnop ou sI oraql '.{5o1o1uoalud .{epo; Jo {ooq}xa[ uerrr]stsfl-Io11.zoql Jo uorlrpa 006I aq+ ur +l€dH dq pasodo.rdauraqas aql .dq paleu$rop d1a1a1d -uroc uaaq seq sprolrlneu Jo uorleagrss€Icaq1 d11uaaa.rplun d11 'soararns slLlx+tlnI{ '.readde ,t1uo r{clqr'/\ Jo e"roua8 na.ouoa.rql dluo orozouaC a{l 'palli '"ra,lamoq'qc1q.u. 's4ao1s uI 5uo1 selt Jo auou alq€ls arour asoru qolqde iuorJ uorlerper aarsua+xa aseqd I€raaos (sr ;o leluoru -r.radxaleillui uB sr aroql |B{? !sru.ro; crozoaled ar{l dq u,{4.oqs u.ra11edle.rauaF oql salecrldnp sprolrlneu arll Jo ,{.ro1srqluocag o} 'pa^rrap crsseJnf ar{J are sprolrln€u crss€rr[-]sod 1e .{pure; srql '1aururn11 'd ' 'qleds ruorJ : ( ggOf : gZ LZ,6T ) se1.1aql olur palrarns auprlrln€uo5ur.idg aql Jo looqs#o uB lei{} ocuoprAaFuo"rls sra#o 'uarou>1 prralaa7 a.o\I Jo uerur€C 0q+ urorJ uaurcads a18uis B lnq 'sproli}n€r ars sprolrlneu ueilaeqg ol{ or{} Jo uor}curlxa alalduroa 'sprouourue lsorulu s€^,!.aroq] (uerloeqg) orssur.r;,olBI aql ul lnq aql roJ se.rd.+l sB spiolrlneu aq+roJ srsrrc;o por.radB lou su.d.uerru 'snoraJruoqreC -Jod aqJi ar{} ur {a€q unbaq spuar} Jo uorleurrulno e .{loraur sr arss?rrJ ai{+ ul sprolrln€u ar{l Jo u"ro11ed.{.reuorlnlorra 'crozoal€d 'eune; aq6 ,t1.reaaql Jo +Bq1o+ pe"redurooSurqlou 1nq

'IOOTOJNOUaYd 88r 896I sfyugulusat{I .{o soJyJS 184 BUITItrETIN: wIUSEUII OF COMPARATWE ZOOLOGY probably also be included in the Nautilida but clear evidence of this relationship is not available (R. II. Flower, personal corn- munication). Flower (1952) u'oultl clerivethe Rutoceratida from the oncoceratida. The Liroceraticlae,Ephippioceratidae, Para- nautilidae, Clydonautilidae, and Gonionautilidae, all formerly plaeed in the lrtrautilida,il&y now neeclto be placeil in a new orcler. At first it would seemthat they would be logically ineluded in the Barrandeoceratida I horver.er,eonnecting forms from the Devon- jan have not been reeognizeclas yet. The status of the Solenoch- ilida, Tarphyceratida, Barrandeoceratida, and Bassleroceratida is a source of disagreement among specialists. The crux of the difficulties and confusion in nautiloid systematics and evolution lies in the great host of ear1l' Paleozoic families. Taxonomic sta- bility of these forms rn'ill be approached as our hnov'1edgeand understanding of their complex morphoiogy and moclesof adap- tation is increased. Agreement on the s;rstematicsof early Paleo- zoic nautiloids is near but is not quite yet a reality. Because of this no phylogenetic chart is presented. It is significant to note that in the past few years very ferv new genera have been establishedin spi(e of the fact that several large new faunas have been describecl. It would be ptreasantto think that possibly we a,renear the iimit of the total number of genera in this order. This observation is encouraging in that maybe now more effort antl thought can be concentrated on critical paleo- biological problerns. Ever since Williarn Smith's great discovery of the usefulness of fossils for correlation and geochronology,the ammonites have played a leading role as a stratigraphic tool. The pioneer 'Waagen, work of d'Orbigny, Oppel, Quensterlt,Mojsisovics, Neumayr and many otirers firmly establishedthe ammonites as the leacling actor in the drama of 1\ esozoicstratigraphy. Likervise the nature of the ammonoid shell and its manner of growth has lent itself beautifully to the pliable minds of evolutionary theorizers. tr'ew people have had rnore influence on the study of fossil cephalopocls than Alpheus llyatt whose whole philosophy revolved around the recapitulation doctrine - a principle not accepted today by most cephalopod students. I{owever, ferv text books of zoology c,r geology fail to illustrate some of Ilyatt's cephalopods demon- strating recapitulation in action. '+q3T.r/f{ '16 'J ('suorlearunruruoc luuosrad '11a4ry 'f 'I ruoJJ sprououru€ snooctlorC uo +"q+ pue . rrro.rJ sprouoruturl 'roIIJli[ 'N '11 'por,rocl crss€Jnf uo leq+ ruorJ sprouotuure arozoaled uo tleq) '6 '"3r9 c13o1oe8 qa€a ur elaua8 prouoruru? Jo raqrunu Suuroqs qde.r8 .reg

OI 0z 0g 0t 09 09 0l 08 00 001 0il 0zl H vu3N3S 091 66rtfl CIONCI|/TWV0tl ruorJ ore zLI asaql Jo :sproronrruBJo B.raua800gI ,{lal€rurxordd€ 'errua8 Jo lBlol € sr araqJ prououurB Jo uorlnqrrlsrp cr8o{oa5 aql uo (6 a.rnFig) qde;8 rBq aql Jo uorlcnrlsuoo oql salqeua €JauaF prouorulu€ Jo Surueala asnoq crruouoxBl luaoal ar{J

.ICOTOJNOOTYd 98I 8S6I UJ,YUTIOJTIIIANI .{O SOJYJS r86 BUIJI]ETIN: MUSEUM OF COMPAR,ATIVE ZOOIJOGY the Paleozoic, 370 from the Triassic, 735 from the Jurassic and 493 from the Cretaceous. Tirere are an additional 1000 generic names that fall into synonomy. The largest number of these involve Jurassic ammonites. The overall distribution of genera confirm commonly held ''monographic views. In spite of specificinstances of highs" and lack of recorcl,it is the opinion of the Treatise ammonoiclauthors that the data reasonably reflect the history of this group of animals. In fact, C. W. \\'right (personal communication), who compiled the list of Cretaceousammonites, found, his data most illuminating as a commentary on the validity of the Cretaceous stages. The most unusual aspectsof the evolutionary history of the ammonoids are the three periods of crisis; during the first two such crises the group nearly became extinct and from but fe'w surviving stocks eyen larger radiations developed until the final extinction of the group irr the late Cretaceous. The two earlier periods of crisis are in the late Permian and in the late Triassic. Several important aspects in the history of the study of ammonoids have greatly influenced our interpretation of ammonoid phylogeny and taxonomy. It is indeed remarkable that not until the 1860'sdid the splitting of the genusAmmonites really begin. The recognition of generic categoriesamong the ammonoids de- velopeclrapidly after that date. Since this early period there have been proposed many taxonomic schemes for the Ammonoidea. Most of these, however, were based on a single character; the suture, sculpture, siphuncle, and length of body chamber have all been used in various manners with little success.IInit systemsof classification invariably ended up by bringing together hetero- chronous homeomorphs. Present interpretation of the relationships of Permian and Triassic ammonoids illustrates this point well. Figure 3 is a bar graph of total genera and new genera (dark stipple) of Permian and Triassic ammonoids. The average evolutionary tempo of Permian ammonoids is only slightly higher than that of the Carboniferous. The most strihing feature is the presenceof only seven genera in the Upper Permian. It should be kept in mind that the number of known fossiliferous Upper Permian deposits is incleedfew. The ammonoid faunas of such classic areas as the 'sprouollllue orss?rJJ,Jo .,trolsrq d"reuorlnloê aq? ur aseqd pazrlrq€]s aq1 sur8aq uersruy aql qll,rtr snqJ 'sprouoturu€ crsserr[ eadd61 pue aIppIR[ aq] Jo ]sotu apnlcur leql saqrure; -.rodns pelrl-8uol lq8la aql osore uaql Jo ^4.0Je ruorJ tnq pa^q -lroqs o"reaseqd a,nrldnea slrl+ Jo sarlrru€Jpue ?raua8 aq1 Jo 1sotr{l 'uBrrurad al€I aql ur uor+OurlxarBou rloql r01J3sprouolulus aql Jo {D€clatuoca.trldn.re oq} ul aseqd lts}uarurradxoaq1 ;o lq8raq aq1 'sprletacrqdo sluasaedarpue aq1 qll^\ orss€rr;, aq] Jo aseclor{], tB 'sprouolulu€ palrBls lBr{1 Jo uorl€nurluoc 3 sr uor}BrpBr srqJ crs -sBrJJ Ja.{A,OTJo SarIrruBJuazop € uBql aroru ,t11oe.rrpureo ,(11oa.rrp asore>Icols prl€raciqdo olqer.rel .{1aura.r1xasrql uord 'ruroJ r{cuoo ur .tlrpqerrel Jo a8ue.r epl^\ € .roqs qolq.!{ sprleJoorqdo aq1 are sprouoluIuBorssBrJJi lsoruJa.M"ol luBpunqs puB uourruoo?sour OqJl 'a"aoBcsrpouax ar{} ur punoJ aq 01 sr sprououure crssBrJJ Jo ,{.r1saoueaq.l '{co}s alau -{ue o} asrr a,rr8 1ou p1p lnq luaurdolalap lsapour d.ral B rlll^{' CTSSBTJJiAr{} Olur Sanurluoo- ABaCB}rJOuOJdar{t - ASaq? 'sarlrrueJradns Jo auo o.r\l ur papnlcur are {ools prlruecalo.rd 'eraua5 aql Jo sprouorurue u€rrurad crss€rrJ ladd;1 pu€ a1p -pIW pue Braue8 prlrleruoF asaql ;o dueru uaa,M.laqfqd"rouloauoq 's>lools Jo sasecsnoJarunu aJB aJaq; orsserJ[ due o1 le.rlsaaue8ur -aq sarlrtu€J plllleluo8 asaql ;o .{ue ;o flqrqeqo.rdrur arll rouutstu Surcur,l.uooB ur palerlsuourap aABr{s.read 69 lsed oql Joô r{leds ',lI 'T '.ra,l,amo11'sarlrrueJ Jo sarlcr"asal aarsuatxa aql prlrleruo8 asaql Suoure d"rlsaoue Jlar{l peq sprouorurue orsserr;, eoddg 'sarFrrrsJ puB alpprlq ,tueur 1eq1 lqFnoql uaaq 5uo1 seq 11 a^g .,tqsprlruecaloed aql pue u€rrurad aq+q sarlrrueJuoâs ,tq palues -a.rda.r 'sprouorurue are sprlrleruo8 aq1 orozoaled;o sdno.r8 urtsru 'sprouoiurue oid.l ar{} JO oiss€rr;, pu€ u€rurod Jo sdrqsuorlelar ar1aua8o1,tqdaq1 Jo uorlela.rdealur or?Brrrruer8erpe sr p a.rn8rg 'paralunoouo sr BUnBJpagrsraarp a3.re1 'u€rturod.radd61 .{11ea.r€ }Bq? uerqldog alpplur oql lr}un }ou s-rlI oql uroJJ crss€rJil aql olur uo sorJrec snua8 auo ,t1ug 'crsstsrJJ Jard.oTor{} Jo se8e xrs aq} roJ e.rauaF ^\au pue e.raua8 IB}ol aql 'Bl?rls s.^loqsg a"rn8rg ;o qde.r5 req ralleirrs aq;, uerrurad radd;1 'a8e 'r-t 'slrsod ourJeru sB acrecs se aJB ueleJacolo Jo asoql le,{l 'rrB#rB -op OrssBrrI lsourroa\oT uappns ts lou s?id.uorlerpBr srq[ 'e.rauaF 8ZI sll qllitr palerlsuoruap IIo^r sr crsserr; ra^M.oTortl ul 'lu"punqB sprouoluluB rql Jo uorl€rpBr aqJt lou arB pusluoaro '.recse8epelq 'sdl11 '.rourr;, 'eJIofO 'a8ueg lseg pue ar{} lleg 'rcoTo.rNosaYd ,gI 8s6r sJYussrugaNl .{o so,tYIS 188 BUITITtrTIN: I,{USEUM O}' COMPARATIVE ZOOLOGY

The great clecline and near ertinction of the ammonoids in the Rhaetian hrrs been knox,n for a lorrg time. From a peak of 140 genera in the Carnian there are left only a few speciesof 5 genera in the I-lhaetian. There is a sharp decline in evolutionary clevelopmentalread;. in the Norian.

l0 20 30 40 50 60 70 80 90 t00lto t20t30 t40 Fig. 3. Bar graph showing total number of ammonoid. genera and new genela (dark stipple) in each stage of the Permian and Triassic.

A single stoch carries through into the Lias to give rise to the great host of Jurassic ancl Cretaceous arnrnonoids. Tire evolutionary patterns of the arnrnonoidsin these tx'o periods is quite unlike that in the Paleozcicor Triassic. Two persisting, slox'ly ei'olving, root-stocks- the Lytocelatina anrl the l?hylloceratina

i- aarleArasuocaq1 uorJ slooqsJJoJo suolleiper paleada;rq8norql Sursree s€ Brrrlruoruruy ar{} Jo s.8uo"rq1alq€.raurnuur aq} pala"rd -ralur aq qcrrl.{\ ur uor}nloafl a^r}Bra}I to i.roaq} slq pasodo;td 's{q1a; pIaJIBS o8e s.reaf 0g aruos aq1 .Sururofpeseas l€}uaul}

'sprouoruIIIB crsst3rJJ/ put? rrBrlu.rod Jo '7 '5L{ uorlnqrr+srp cr5oloa8 puu fuo5olfqd porrag:ur Sur.ttoqs rut.r5erq

r o{ ?nPw nxaJ o tndas, T ;'49 nL EU;U?nsA7 m fr wr.fivlstcon:x,W^ CL 3 *ffiTr \uduru*asa- V,x n f# FUn'*U uF P z c tt !t U\ai-Axn* o ;"s VaUr U o ..--___ :----- 3WCYIYUls0)lllno z. UI cl o OEvt Y4Q 2eW---vs uau4 2 o -u='E\uut .D o a_" ll iU*u-**?'V a o F 6' = O d(/ * J Cl. o ov 3 ;A=. o 6Vt r o *nFG r/4 * (A * 6' u P- F o - o o e g -t --.1 6' l> <> C) rn l> ;o tYl ct J

(Do 6' a

-uoorda aql uT lrrepunqu lsoru oJB BrauaF paluaurelrJoJo snocurl -so{qoBrl aq; 'sruroJ pallaqs q1oorusro snoce.r}soralaq} ore .{oql !s,{q}al }rralcue ar{+Jo cr}srra}c€reqca.re €rrrleracoll{r{d pue BuT} -erecoldrl aq;, 'paarrap are sprouorutuesnoacelarC pue orssernf Jo lsoq 1ea.r8aq? qarr{Ir ruorJ srro,\Jasard"reuorlnlorto or{} aJe -

68I 8S6r'r0o'rorl{Og.ryd uJyustrJu[aNr,{o s0.tyJs 190 IIUITITETIN: MUSEUM OF COMPARATIVE ZOOIJOGY

stocks. Deciphering the countless threads connecting the Am- monitina and these conservative stocks is still evasive. More

lelocslrichlion ITINA

Componion

Sanlonion

s Coniocion \ \ furon ion

Cenomonion

Al bion z Aplio n F s 8o rrcmio n G s Hou I erivion \ lrl Volonginion () Infrovo lo noin mt o J Purbeck ion o J Porl londion F IO - \ Kimcridgion \ .{.iI c.*r.'.'. o. t r.'.'. Orfordio n 1 t:::: Callov ia n s Eolhonion \e t\ s Sojoc lo n I Toa rc io n 5: $Plicnsbochio n ll3^.."" F \ Sinem urion q' Heffongion W: nhqel io n s \t ion qs Corn \ Lodlnnn

R isio n \ An

$ Sctl h io n Fig. 5. Diagraur showing inferrecl phylogeny and geologic distribution of Mesozoic ammonoicls. (Arlaptect from Arkell 1950, Wright 1952, aacl Kummel f952). '(uorlearunurruoc '.tro1s IrssoJar{} Jo ssaualalduoouraqJ luuosrad 'T) -rleg sITSSoJsB ul\ou{ d11en1ce}ou ar€ }Br{} Braua8 -{ueur ;o 'u.nou4 acualsrxo snor.r.a.rdaq1 .,t1dun sruroJ lrssoJlsaJeau aql tuoJJ 'eune;: luara#rp d"ra.r.ar€ Braua8 nqt ;o ^,tueurler{} }oBJ ar{} pu€ 'luacag +uaoag yo dlrs.ronrp 1ea"r8aq;, oq? urorJ ,t1uo urnou4 'elerqouerqlq ar€ 8eI ;o e.raua8996 dlalerurxoeddearn Jo !e.rauoE luocag Jo raqunu 1ea.r8aql sI 9 e"rn8rg yo ure.r8elp req er{?Jo 'B]Brr{cuerqrcl arnl€oJ ,o'ur>F"r1slsolu aq'l g:oe;raua8 ;o uoflnQlr]slp

'.cl'ols.rrug 'T 'po1.red ('uorlearunuruoo leuos,rad rtroJJ tstr€C) 'EI.{ crEoloe8 qc€a ur t.rauaE qcutsrqrp Jo raqunu Eur.er.oqsqder8 reg .g

VU3N39 tA SlvlHcNVUgto ool hl tbl arurl oql uo ts1ep alerurxordde pue a^rleluel paqsrurnJ ,(IpuI{ 'rJ 'sprouorurrrB ^,l\olsrrBg arISaT [ puB sprolr?n€u oq? s3 ooll -uallu apld&sB pa,\racarlou aABqspodoleqdao Blerqouerqrq aq; 'surlruoluruy raproqns aql Jo uor+scglpour roJ paau aq ilI^r arar{1s{Dols-?oor aarlB^rasuoc ar{? Jo rar{}o aq} ro auo ol poil flalruyap ororu aq u?c sarltueJradns snoac"?arC 'crss€rnf pue crsssJnf snorrsa aql JI puB uarllv[ ar{} Jo asoq? Wlm ueql salluolulu€ snoaoelarC l{}lrv\ ap?ru uaaq suq sso.rSoed

'LOOTO.tNOgTvd I6I 896I g'tryustrJufiaNl .{o sofyJs t92 BUIJLETIN: MUSEUM OF COMPARATIVE ZOOLOGY

recor{alof the dibranchs does not make them a suitable group for the study of evolutionary rates. The present status of our knowledge of the fossil Cephalopoda presents an encouraging framervork to direct and guide future research. The great successto which the cephalopods,especially ammonoids, have been used in stratigraphy has resulted in the major emphasisbeing placed on them as "tools" of stratigraphy. It is becoming more and more clear that a greater und.erstanding of the animal and its ecology and adaptive range wilt add greatly to the value of the Cephalopo,ilaas "tools" of stratigraphy and as "tools" for study of evolutionary processes.

BEFERENqES ABru"L, W. J. 1950. A claseiffcationof the Jurassic ammouites. Jour. Paleontology, vol.24, pp. 354-364. Fr,ownn, R. I[. L952. The ontogeny of Centrooeras,with renarks oa the phylogeny of the Ceutroceraticlae.Jour. Paleontology, vol. 26, pp. b1g,b28. Fr,owna,,R. 8., antl B. Kuarunr 1950. A classification of the nautiloids. Jour. Paleontology, vol. 24, pp.604-616.

Kuuuu,, B. L952. A claseification of tho Triassis ammonoitls. Jour. Paloontology, vol. 26, pp. 847-853. 1953. The ancestry of the family Nautiliclae. Breviora, No. pl, pp. 1-8. Spens, L. F. L927, Revision ol the Juraseic eephalopotlfauna of Kachh (Cuteh). Mem. Inclia Geol. Survey (Palaeontologia Inrlica), n. ser., vo,l.g, mem.2, pp. 1-8{ ple. 1-7. Wnrcur, C. W. L952. A clagsificationof the Cretaceousammonites. Jour. Paleontology, vol.26, pp.2L3-2,22.