Observations on the microscopic shell structure of Spirifer cuspidatus, Sowerby, and some similar American forms

NATURAL

SCIENCES OF

PHILADELPHIA. 275

Observations on the Microscopic^ShellStructure^of

SPIRIFER

CUSPIDATUS, Sowerby, andsomesimilarAmericanforms.

BY

F. B.

MEEK.

In hisvaluableandaccuratelyillustratedworkon theBritishCarboniferous Brachiopoda, page45,Mr.Davidsonstates that Spirifer cuspidatus,Sowerby,

"belongs^tothe genusSpiriferproper,andnot tothe subgenusCyrtia," as heandothershad_supposed.

He

alsoadds that" no _specimenof S. cuspi- datusIhave hitherto beenable toexamine, has exhibited a deltidium ^inits entire condition,but which,^inallprobability,wasnot perforatedby^acircu- larforamen,^asseenintrue types^ofthesubgenusCyrtia." Inanoteatthe bottomofthe page containing^hisexplanationsof plateviii.,however,ofthe samework, he^correctsthe above statementasfollows: "At_page45,Istated thatno specimenof S. cuspidatus^Ihad hithertobeenable toexamine pos- sesseditsdeltidium,andthatIconsidereditwas,^inallprobability,potper- foratedby^acircular foramen,^asinthe true types^ofthe subgenusCyrtia.

Subsequently, however, Mr.^S.P.

Woodward

showed

me

the internal cast of the ventral valveof aspecimen ⁱⁿtheBritish Museum,thought ^tohavebe- longedto S. cuspidatus,andderived from the Dolomitic carboniferous lime- stoneofBredonHill,inwhich there is evidence that the deltidiumwasin realityperforatedby^{a circular}foramenas inCyrtia." Ofthisinternal cast, aswell as of agutta-perchamould

made

from_it,Mr.Davidson_gives good figures,on plateix. (figs.1andla) oftheworkabovecited.

From

these remarks,andtheaccompanying figures,^itseemedtobe nearly or quite demonstrated, thatS. cuspidatus ^isa trueCyrtia, as had formerly been supposedby^Prof.

McCoy

andMr. Davidson, and,asitisalsothe type upon which Sowerby had^{founded his older}genusSpirifer,^itwouldfollow, asamatterof course,thatCyrtia,Dalman,could only be regarded^asan exact

synonym

^ofthetypical section of Spirifer,Sowerby,whichviewwasadoptedⁱⁿ theworkon the Palaeontology^oftheUpper^Missouri,by^thewriterandDr.Hay- den. Itwillalsobe observedthattheshell structure of Spirifer^istherede- scribed asbeing impunctate,ⁱⁿaccordance with the views ofDr. Carpenter and Mr.Davidson inregard^tothe group^towhich we proposeto restrict

it, after separating, generically,the punctate typesSpiriferinaand Cyrtina.

Some

examinationsIhave_recentlyhad anopportunity^tomake,however, oftheshellstructure and internal charactersof several American forms, closely alliedto,ifnotinsome instancesidentical with, Spirifer cuspidatus, as well as of a supposed authentic ^British example^ofthat species, inthe collection ofMr.Worthen,at Springfield,have_givenrisetodoubtsinregard tothecorrectness ofsomeofthese conclusions.

Iwasled to

make

these examinations byobservingⁱⁿMr.Worthen'scol- lection excellentspecimens, apparently^ofSpirifercapax,Hall,(very^similar to S. cuspidatus, Sowerby) from Clarksville, Missouri, showing exactly tho form and internal characters of agenus Syringothyris, proposed by ^Prof.

Winchell,ⁱⁿthe Proceedings^oftheAcademyforJanuary,^{1863. It will}be remembered that Prof.

W.

described the type^{of this} genus^as having the formand general external charactersof Spirifer cuspidatus,but differingin the possession^ofacurious internaltubeconnected with the innerside ofa kindofdeep-seated,^false deltidium, ^ortransverse_plate passing ^acrossbe- tweenthe dentallaminae. Healso states thattheshellstructureisimpunctate.

On

examiningthe specimens above alluded^toinMr. Worthen's collection, Iatonce observedtheirexact agreement^inallinternal characters, as well as iuthe form, ornamentation,&o.,withSyringothyris,but soon saw, while^look- ing^atthemwithagool pocketlens,someevidencesofapunctatestructure, and, on afterwardsplacing fragments ^ofthe shellunderahigh magnifier, wherethey could beexamined bytransmitted _light,they were found ^tobe beyond^doubtpunctate. Subsequently^Imentionedthis fact to Prof.

Win-

1865.]

276 PROCEEDINGS

OF

THE ACADEMY OP

chell, atChicago, and _requested

him

tore-examinehis typicalspecimens of Syringothyris, to see if he could discover any ^{traces of} punctures.

He

afterwards informed

me

thathehad done_so,hut could seeno evidences ofpunctures,andhe kindly gave

me

aslip of glassupon which^{wetefastened,} withCanadabalsam, fragmentsof his typical speciesandofanother not yet described, inneitherofwhich anypunctureswerevisible.

Inthisconnection, however,^itisproper^toremark, that^allofthesefrag- ments^{are either}verysmall, or soopaque andbadly preserved, that the punc- tures might ^notbe apparent, even^ifihey^{exist. Itis also}worthy^ofnote that in several shells of thistypewhichIhaveexamined, the punctures^arevery small,andsodistantthat fragmentslargeenough^toshowclearly thepunctures asseeninthevarious typesof Terebratulidce,might^{be without}a singlepunc- ture.

From

thesefacts,andotherstobementionedfarther on,^I

am

strongly inclined to think Prof.Winchell's specimens ^are not in a good condition forshowing ^theshell structure,andwithout intending^toattributeany^care- lessness orwantofdiscriminationtothat gentleman, that^tjiesespecies

may

yet be found^tobe punctatewhenother specimensⁱⁿa better state of preser- vationareobtained.

On

_lookingfartherthrough Mr. "Worthen'scollections,Isawotherspecies of this type,and examined their shell structure withthe following^results: first, a form from Missouri, believed to be Spirifersubcuspidatus, Hall, from the

Keokuk

division ofthe subcarboniferous _series,(andthought by Mr. Davidson, fromanexaminationofexamplesfromIllinois,tobeidentical withEuropean^{formsreferredtoS.}cuspidalus),wasexamined,andfoundto be unquestionably punctate. Thepunctures ^aresmall and scattering,but owing^tothefactthat they were,ⁱⁿthe specimens examined,^filledwitlidark opaquematter, they could be veryclearlyseenbytransmitted_light, inthin fragments saturated withCanadabalsam. Theinterior of this shellis

unknown

tome.

Next, specimens^ofapparently anotherspeciesor variety, (scarcely,^ifat all,distinguishable,by^{externalcharactersat}least,fromcertainformsof S.

cuspidatus as usually understood), from the fine-grained sandstone ofthe Knobbs,backofAlbany, Indiana, were_examined, andalsodiscoveredtobe clearlyandunquestionably punctate, the punctures being smalland scatter- ing as in^{the. last.} Internal casts of this_shell,from thesame locality,show

ittopossessexactly the internal charactersofSyringothyris, Winchell.

Having thus found the punctate ^structure clearlyvisiblein the several Americanforms mentioned,^aspecimenof S. cuspidatus,sentby^Mr.Davidson toMr. WorthenfromMillicent Island,wasexamined,andquiteunexpected- lyfoundtobealso clearlypunctate,^liketheAmericanforms. ThisIrish speci-

men

^{isnotinaconditiontoshowthe}interior,butonremoving some^ofthema- trixfrom the foramenitwasfoundto possess,near thebeakat_least,thetrans- verse_plate,ordeep-seated ^falsedeltidium, seenin Syringothyris,though^itwas impossible^todetermine, without spoiling the specimen,whetherornot the characteiistictubeexists inconnection with^itsinnerside.

Now whenitisrememberedthat as careful, conscientious,andaccuratean observeras Dr.Carpenter, haspronounced thestructure of Spirifer cuspidatus impunctate,*aftera thorough examination, the question naturally suggests itself,whethertheremaynot be twoclosely similar,but reallyverydistinct, Britishtypes confounded under thesingle specificnameS.cuspidatus? that

is,one with a punctate^structureandanother withoutit. If so,andthe punctate structure^ishere, asI

am muchinclined to believe,coincident with the pecu-

* Afterspeaking^{of the}factthatMr. Davidsonhail,onothergrounds, divided theSpirifer groupinto sections,whichitwasalsofoundcouldhe distinguishedbytheir shell structure, Or.

Carpenter remarks^that"underthesubgenusCi/rlia,he_{[Mr.Davidson]}places theseimpunctate species,which,^{like C.}Irapczoidalis.havea perforation^forthe pasi-age of a pedicle; besides these tpecies1haveexamined C.cuspidata,[=Spirifer cuspidatus,]h:h1amfullysatisfiedthat in neither of thesedo anyperforations exist." (Davidsoii's IntroductionlotheClassificationof^t/t*

Bradneipuda,p.^C4.

[Dec.

NATURAL

SCIENCES OP

PHILADELPHIA.

277

liarinternalcharactersof Syringothyris,^itbecomesamatterofsomeinterest to

know

_{upon which}ofthese typesSowerbyformed the genusSpirifer. ^Ifit was upon^theone with a punctate structureandaninternal tube,then Syringo- thyriswould apparently beanexact

synonym

^ofthe genus Spirifer,which woulddifferfrom the ordinary types usuallyreferred tothat genus, such^as S. striatumforinstance,

(=

Trigonotreta, groupof Koenig,)aswidely^asthe latterdiffersfrom _Spiriferinaand _{Cyrtina. If,} on thecontrary,Sowerby's typewasan impunctate^shellwithouttlieinternalcharactersof Syringothyris, or inother words aTrigonotreta,thenSyringothyriswouldstandasadistinct group,differingfrom_Spiriferproper^inasimportant characters^asthosedis- tinguishingSpiriferinaandCyrtina.

Since seeingsomeoftheinternalcastsof Syringothyris, inMr.Worthen's collection,showingthe peculiar appearances producedbythe impressions^left by^{thefalsedeltidium}anditsattachedinternal tube,^Ihavebeen struck with their similarity tothe_figuresgivenbyMr. Davidson, (onplate^ix.of hiswork alreadycited), of an internal cast of a supposed exampleof S. cuspidatus, thought^toindicatethe presence^ofaperforation through the deltidium. ^It isalsoworthyofnote that Mr.Davidsonrefersthisspecimen^toS.cuspidotus with doubt,andsays ^itdenotes the presence^{of a} "tubular"perforation.

Hence,^I

am

_very

much

inclined tothe opinionthatitrather indicatesthein- ternalcharactersofSyringothyris,than of an actualperforation through the deltidium,^{as in} Cyrtiu,*and thusseems tosustainthe view that there

may

beatleasta part^ofthe Britishspecimensreferred to S. cuspidatus,possessing the internalcharacters of Syringothyris. This opinionreceives furthersup- port, too,from the fact that Prof.McCoy,ⁱⁿ describing ^5. cuspidatusfrom Irishexamples, says^ithasan"

internal,deep-seated pseudo-deltidium, with- outperforation,leaving onlyan_openingatitsbase."

Itistobehoped^thatthose

who may

^have duplicate authentic ^Britishex- amples^ofSpirifer cuspidatus,

may

^{be induced to}

make

sections across the beakof the ventral valve,with the viewofascertainingwhetherornotany ofthem have the internaltube of Syringothyris, and ifso, to ascertain whetherthe punctate^structureiscoincidentwith the presence^{of thisinternal} appendage.

It

may

be proper^torepeathere,fortheinformationofthose

who may

^b disposed^to

make

suchobservations,thatin alloftheseshellsIhaveexam- ined,the punctures^areverysmall, scatteringandnot arranged with the regu- larityseenⁱⁿmust_typesof Terebraiulidie,orinCyrtina, Spiriferina, &c.

Where

theyhappen,^{as isoften}the case, tobefilledwithmatterofthesamecolor andtranslucency^asthefiberscomposingtheshell, it isexceedingly^difficult toseethem.

When

very small fragments only^areexamined, they

may

^like- wise be readilyoverlooked,^asthe fragment

may

^{contain but oneortwo of} them,ⁱⁿwhichcasethey might notattract attention.

Where

_theyarefilled, however, withdarkoropaquematter,andafragment, say 0"03^ofaninchor moreindiameter,^isexamined with a moderately low power, they^arevery distinctly seen,andcannot be for a

moment

mistaken for any appearance producedbya merely^{accidentalcause.}

Note. It

may

^{not be outof}place ^to add _here,thatthewriter and Mr.

Worthenhaveascertained that theCoal-measurespecies,Spirifer hemiplicatus, (Hall,)^isadistinctlypunctate shell,andthatithas not theinternalcharac- tersof Spirifer or Spiriferina,but thoseof Orthis,excepting^thatthereare in the ventral valvethreeprominent, verycloselyapproximate,andnearly par- allellaminae,extending from thebeakforwardtonear the middleofthe valve.

Hencewe_regarditasthe type^ofanew_{group,probably a}section ofthegenus Orthis,forwhich we haveinMSS.proposed the

name

Synjrilasma,M.

& W.

* Itisnut improl able,however,that the tubeinSyringothyrismayhave sometimes,ⁱⁿyoung shell,been connected withan externalopeningthroughthe deltidium,though noneof the speci- mens1haveseenBhows such au_opening.

1865.]