Herausgegeben

GE RL von Wu

Bet 0 I Heft 57.

— Zweiundzwanzigster Band. ——-

BE 6% ET Fünfte Lieferung

RL EROR Inhalt: | 2
Ips Altis, ne The Cranial a of me Mail-cheeked Fishes. Lig. 3.
Er Mit 2 Tafeln. |

STUTTGART.

erbartsche Verlagsbuchhandlung, Nägele & Dr. Sproesser.
| A 1909.

a en ne ee ee u a orkan hast
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Herbst 1909

a nn

ZOOLOGICA

Neu -Erscheinungen
sowie hervorragende

Periodica und Werke

der letzten J ahre

E. Schweizerbart’sche Verlagsbuchhandlung
Nägele & Dr. Sproesser, Stuttgart

Hochgeehrter Flerr !

Wie alljährlich, so möchten wir uns auch jetzt wieder
erlauben, Ihre Aufmerksamkeit auf die in unserem Verlage er-
scheinende

Zoologica

Originalabhandlungen aus dem Gesamtgebiete
der Zoologie

herausgegeben von

Prof. Dr. C. Chun in Leipzig

zu lenken und dafür Ihr gütiges Interesse zu erbitten.

Wie Sie aus dem beigefügten Verzeichnis ersehen
wollen, sind auch im verflossenen Jahre wieder mehrere her-
vorragende Monographien der „Zoologica“ angereiht worden,
resp. befinden sich z. Zt. in Vorbereitung. Wir würden es daher
dankbar begrüßen, wenn auch Sie sich immer mehr von der
Wichtigkeit der „Zoologica“ und der in ihr erscheinenden tief-
gründigen Monographien als unentbehrliches Nachschlagewerk
bei Ihren Arbeiten überzeugen wollten und sich daraufhin zu
einem Abonnement auf diese hervorragende Zeitschrift oder
auch zur Anschaffung der einen oder anderen Abhandlung
entschließen könnten.

Für diesen Fall erlauben wir uns, Sie noch ergebenst darauf
hinzuweisen, daß wir bereit sind, die „Zoologica“ bei Abnahmeder
ganzen Serie von Heft 1—53, 541, 585—57 statt Mk. 2752.— zu
Mk. 1500.— abzugeben, sowie auch auf eine größere Anzahl
Hefte erheblichen Preisnachlaß zu gewähren, um neu hinzukom-
menden Abonnenten die Ergänzung der ganzen Serie oder auch
die Anschaffung älterer Hefte nach Möglichkeit zu erleichtern.

Indem wir noch die weiter aufgeführten Werke unseres Ver-
lages Ihrer geneigten Beachtung empfohlen halten, zeichnen wir

Hochadhtungsvoll ergebenst

Stuttgart, _ E. Schweizerbart’sche

Herbst 1909 Verlagsbuchhandlung
Nägele & Dr. Sproesser.

31

Spuler, A., Die Raupen der Schmetterlinge Europas. Zweite
Auflage von Dr. E. Hofmanns gleichnamigem Werke,
60 Tafeln mit über 2000 Abbildungen. Brosch. Mk. 20.—,
geb. Mk. 28.—.

—— Diese beiden Werke von Spuler, die zum ersten Male auch die Klein-
schmetterlinge in Bild und Wort umfassen, erfüllen alle streng wissen-
schaftlichen Anforderungen, sind ganz auf die Höhe der Zeit gebracht und
bilden für jeden Fachmann ein unentbehrliches Nachschlagewerk.

*Stahr, H., Über die Papillae fungiformes der Kinderzunge und ihre Be-
deutung als Geschmacksorgan. (Sep. a. Zeitschr. f. Morph.) Gr. 8°.
1901. 62 S. Mit 4 Tafeln. Mk. 3.20.

*Stejneger, L., Batrachians and Reptiles. (Siehe unter Reports of the
Princeton University etc. vol. 11.)

*Stieda, L., Das Gehirn eines Sprachkundigen. (Sep. a. Zeitschr. f. Morph,)
Gr. 8°. 1907. 56 S. Mit 1 Tafel. Mk. 2.—.

*Stuzmann, J., Die accessorischen Geschlechtsdrüsen von Mus decu-
manus und ihre Entwicklung. Gr. 8°. 1899. 38 S. Mit 1 Tafel.
Mk. 1.20.

Taschenberg, O., Weitere Beiträge zur Kenntnis ectoparasitischer
mariner Trematoden. Mit 2 Tafeln. 4°. 1879. Mk. 3.60.

— Die Flöhe. Die Arten der Insektenordnung Suctoria nach ihrem
Chitinskelett monographisch dargestellt. Mit 4 Tafeln. Gr. 8°,
1880. Mk. 7.—.,

— Die Lehre von der Urzeugung sonst und jetzt. Ein Beitrag zur
historischen Entwicklung derselben. Gr. 8°. 1882. Mk. 2.—.

— Historische Entwicklung der Lehre von der Parthenogenesis.
Gr. 4°. 1892. Mk. 3.—.

— Geschichte der Zoologie und der zoologischen Sammlungen an
der Universität Halle. 1694—1894. Mit 8 Tafeln und 3 Textfiguren.
Gr. 8°. 1894. Mk. 6.—.

Thiele, R., Die Blutlaus (Schizoneura lanigera Htg.). 70 S. Mk. 1.—.

*v. Török, A., Inwiefern kann das Gesichtsprofil als Ausdruck der In-
telligenz gelten? Ein Beitrag zur Kritik der heutigen physischen
Anthropologie. (Sep. a. Zeitschr. f. Morph. Gr. 8°. 1901. 134 S,
Mit 3 Tafeln. Mk. 5.—.

*y. Török, A., Neue Untersuchungen über die Dolichocephalie. (Sep.
a. Zeitschr. f. Morph.) Gr. 8°. 1905. 24 S. Mit 2 Tafeln. Mk. 2.60.

*— Über einen neueren Fund von makrocephalen Schädeln aus Ungarn.
(Sep. a. Zeitschr. f. Morph.) Gr. 8°. 1904. 60 S. Mit 6 Textfiguren.
Mk. 1.60.

*Volk, R., Über die Elbuntersuchung. (Sep. a. Archiv f. Hydr.) Gr. 8°.
1908. 10 S. Mk. —.60.

*Weigelt, C., Beiträge zur chemischen Selbstgesundung der Gewässer.
(Sep. a. Archiv f. Hydr.) Gr. 8°, 1907. 22 S. Mk. —.80.

Weinberg, R., Die Gehirnform der Polen. Eine rassenanatomische
Untersuchung. Mit der Großfürst Sergei-Prämie des Internationalen
Archäologischen Kongresses preisgekrönte Arbeit, Gr. 8% 1905,
235 S. Mit 30 Figuren auf 19 Tafeln. Mk. 30.—.

— Die Gehirnwindungen bei den Esten. (Eine anatomisch-anthropologische
Studie.) Mit 5 Doppeltafeln. 1896. 96 $. Mk. 27—.

Weiß, B., Entwicklung. Versuch einer einheitlichen Welt-
anschauung. 8°. 207 S. 1908. Mk. 3.60.

*Whipple, J., The Ventral Surface of the Mammalian Chiridium. (Sep.
a. Zeitschr. für Morph.) Gr. 8°. 1904, 108 S. Mit 54 Textfiguren
und 2 Tafeln. Mk. 3.60.

* Zacharias, O., Über Periodizität, Variation und Verbreitung verschiedener
Planktonwesen in südlichen Meeren. (Sep. a. Arch. f, Hydr.) Gr. 8°,
1906. 78 S. Mit 23 ‚Abbildungen. Mk. 2,—.

Zimmermann, H., Tierwelt am Strande der blauen Adria. 8°. 30'S.

Mk. —.60.

*Zuckerkandl, E., Über die palmaren Tastballen von Myopotamus coypus.
(Sep. a. Zeitschr, f. Morph.) Gr. 8°. 1906. 8 S. Mit 1 Tafel. Mk. —.80.

*— Über laterale Rachentaschen bei Lagostomus trichodactylus. (Sep.
a. Zeitschr. f. Morph.) Gr. 8°. 1906. 9 S. Mit 2 Textfiguren und
1 Tafel. Mk. —.80.

tafeln. Mk. 2.40.

*— Zur Morphologie des Affengehirns. Dritter Beitrag. (Sep. a. Zeit-
schrift {. Morph.) Gr. 8°. 1904. 38 S. Mit 11 Textfiguren und
1 Doppeltafel. Mk. 1.60.

*— Zur Morphologie des Affengehirns. Vierter Beitrag. (Sep. a. Zeitschr.
f. Morph.) Gr. 8°. 1904. 23 S, Mit 2 Textfiguren und 1 Doppel-
tafel. Mk. 1.20.

E. Schweizerbart'sche Verlagsbuchhandlung

Nägele & Dr. Sproesser :: Stuttgart

nn nn nn I.

en

Soeben erschien in unserem Verlage:

LEHRBUCH
der Vergleichenden Anatomie
der Wirbeltiere

von

Dr. W. Schimkewitsch

ord. Professor der Zoologie und vergleichenden Anatomie, Direktor des Zoologischen
Instituts der Universität St. Petersburg

Mit Genehmigung und Unterstützung des Verfassers ins Deutsche übertragen
und bearbeitet von

Dr. H.N. Maier und B. W. Sukatschoff

München £ Dorpat.

Gr. 8°. 650 Seiten mit 635 zum großen Teil farbigen Textabbildungen in 971 Einzeldarstellungen.
Preis brosch. Mk. 18.—, geb. Mk. 19.50.

er bedeutende Ruf, den der Verfasser als vergleichender Anatom überall in Fachkreisen

geniesst und die besonderen Vorzüge seines Lehrbuches gegenüber andern ähnlichen

Publikationen veranlassten Übersetzer und Verleger, von dem obigen Werke eine deutsche
Ausgabe zu veranstalten. Welchen Anklang die neuartige Behandlung des Stoffes durch Professor
Schimkewitsch gefunden hat, möge aus der Tatsache hervorgehen, dass nach kurzer Zeit von der
russischen Ausgabe eine zweite Auflage in Angriff genommen werden musste. Am besten aber
werden die Ziele, die der Verfasser mit seinem Werke verfolgt hat, aus dem Vorwort ersehen
werden können, das wir umstehend auszugsweise wiedergeben. Ganz besonders möchten wir
noch darauf hinweisen, dass dem Buche zum ersten Male farbige Abbildungen beigegeben
sind, wodurch das Verständnis der Materie wesentlich gefördert werden dürfte. Trotz der
reichen Illustrierung und der schönen äusseren Ausstattung haben wir den Preis für das Werk
sehr niedrig angesetzt, um die Anschaffung desselben nach Möglichkeit zu erleichtern. Wir
bitten daher das Buch freundlich aufnehmen und speziell die Studierenden auf dasselbe hin-
weisen zu wollen.

Das Werk wird von jeder Buchhandlung gerne zur Einsichtnahme zur Verfügung gestellt.

Hochachtungsvoll

E. Schweizerbart'sche Verlagsbuchhandlung
Nägele & Dr. Sproesser

STUTTGART, im Dezember 1909.

Aus dem Vorwort des Verfassers:

Bei Abfassung des vorliegenden Lehrbuchs habe ich mir
die Aufgabe gestellt, den Studierenden einen kurzen, aber
doch möglichst vollständigen Leitfaden für das vergleichend-
anatomische Studium der Wirbeltiere zu geben.

In der Annahme, dass die Überladung der Lehrbücher
durch secundäre Details manchmal nicht nur einen über-
flüssigen Ballast bildet, sondern das Studium ausserordentlich
erschwert, da der Anfänger meist nicht in der Lage ist,
das Wesentliche von dem Unwesentlichen zu unterscheiden,
habe ich mich bemüht, diese Überladung zu vermeiden und
die Hauptzüge in den Vordergrund zu stellen. Deshalb
geht der speziellen sachlichen Beschreibung der einzelnen
Organsysteme oder ihrer Teile eine kurze anatomisch-

Fig. 47. embryologische Übersicht voraus, in welcher ein ganz all-
Embryonalhüllen eines Säugetieres. al — Allantois, am — £ : R h ö
Amnion, amh. — Amnionhöhle, d — Darmhöhle, do — Dottersack, ect — gemeines Bild für das betreffende System oder seine Teile
Ectoderm, ent — Entoderm, mes — Mesoderm, s — Serosa, 2.p. — Zona

pellueida (Prochorion). Derivate des Ectoderm braun, Mesoderm rot, entworfen wird; zugleich soll ein theoretischer Standpunkt
Entoderm grün. [Nach TURNER.]
gegenüber dem Behandelten gewonnen werden. Es muss
daher öfter in der ausführlichen Behandlung manches von dem wiederholt werden, was in der allgemeinen
Übersicht schon erwähnt war. Diese Wiederholung bezieht sich aber nur auf die Hauptzüge, deren nochmalige
Erwähnung ganz nützlich ist.

Von dem Gedanken ausgehend, dass das ausführlichere Studium irgend eines bestimmten Organsystems
in didaktischer Hinsicht von grosser Bedeutung sein kann, halte ich mich etwas länger bei der Vergleichenden
Osteologie auf, um so mehr, als die Bekanntschaft mit dieser Abteilung der Vergleichenden Anatomie am
leichtesten durch das praktische Studium der Skelette in natura begründet werden kann.

Ich glaube, dass die theoretische Beleuchtung nicht nur das Studium erleichtert, sondern sie allein das
Verständnis für die zu studierenden Tatsachen und deren Bedeutung ermöglicht. Deshalb wurde nirgends von
dieser Behandlungsweise abgewichen, da ich es für besser halte, theoretische Betrachtungen einzuflechten, selbst
wenn diese noch nicht ganz vollständig sind.

Bezüglich der Art der Behandlung konnte ich zwei Wege einschlagen. Den einen Weg zeigen die Lehr-
biicher von GEGENBAUR und von WIEDERSHEIM, welche bei der Beschreibung die Organsysteme manchmal
sehr in ihre Bestandteile zerlegen und die Beschreibung des einen oder anderen Organes bei allen Gruppen der
Wirbeltiere in aufsteigender Reihenfolge geben. Bei einer derartigen Be-
handlung treten die genetischen Beziehungen und die allmähliche Kompli-
zierung eines Organs mit allergrösster Deutlichkeit hervor, dafür aber geht
die anatomische Physiognomie der einzelnen Gruppen vollständig verloren.
Letzteres wird dagegen sehr gut auf dem zweiten Wege erreicht, dem HUXLEY
und in der neuesten Zeit PARKER und HASWELL folgten, die eigentlich
eine anatomische Beschreibung einzelner Gruppen geben. Bei dieser zweiten aus, 5% -- v
Behandlungsweise tritt die ersterwähnte Seite vollständig in den Hintergrund |
und statt eines Lehrbuches der Vergleichenden Anatomie erhält man ein
Lehrbuch der Zoologie auf vergleichend-anatomischer Grundlage. Dagegen
kann man natürlich einwenden, dass die Charakteristik der Gruppen nicht
die Aufgabe der Vergleichenden Anatomie bildet. Vom theoretischen Stand- 2 = 34.
punkte aus kann’man dem nur zustimmen, in der Praxis aber muss man paratand des Biastopon. Bee

Dorsalrand des Blastoporus, d.p. — Dotterpfropf,

n : & 4 ae 5 t — Ectod ‚ J.h. — Furch höhle, es
mit der Tatsache rechnen, dass nicht selten bei dem Universitätsunterricht “ ne De

Q S “ 5 5 Er ö c R Die Ränder des Blastoporus umgrenzen den
die Kenntnis der Wirbeltiere hauptsächlich nur auf einem vergleichend- Dokferpfropk: Oben der en sun Gesine

= x 2 . A 6 erweiternde Gastralspalt. Ectoderm braun, Meso-
anatomischen Studium derselben beruht, als dem wichtigsten und reichsten nn EöR Entodermrerhi: [Nach 0. HERTWIG.]

I mes

hinsichtlich seiner Ergebnisse.
Deshalb darf meines Erachtens
-ep einLehrbuch der Vergleichenden

Be Anatomie das zweite Ziel, näm-
lich dem Studierenden auch

eine gewisse Vorstellung von

der anatomischen Physiognomie
der einzelnen Gruppen zu geben,
nicht ganz ausser acht lassen,
um so mehr, als bei einer zu
weit gehenden Einteilung der
Organsysteme in der Beschrei-
bung manchmal die Einzel-

heiten das Ganze verdecken.
Fig. 80. DE BEE KESE 5 R
Gallus (Huhn). Federentwicklung: Mit Rücksicht hierauf wählte
A — erste Anlage der Feder im Längs- 5 .
schnitt, B — Enas weiter enforickäite ich den Mittelweg, und zwar
Anlage im Längsschnitt, C noch . n . Be .
weiteres Stadium im Längsschnitt. b1.g. indem ich eine ausiührlichere
— Blutgefässe, cor — Corium, ep — Epi- . . -
dermis, pa — Coriumpapille. [Orig Vergleichende Beschreibung ein-
D — schiefgeführter Querschnitt durch B
eine der Fig. C entsprechende Anlage, zelner Systeme und deren Teile
E — Querschnitt durch den oberen Teil = - - 5
einer entwickelten Anlage vor dem Aus- gebe, bemühe ich mich, die-
schlüpfen, mit schon ausgebildeten Strah- D
len; Cy.s. — Cylindrische Schicht der Epi- selben nicht allzusehr zu zer-
dermis, Ep.s. — epitrichiale Schicht, As — Federscheide, /nt — Zwischen-

schichte der Epidermis, — PCoriumpapille (Pulpa), S — Strahlen der Embryo- legen. So werden z. B. alle
naldune. — Derivate des Ectoderm braun, Mesoderm rot. [Nach DAVIES.]

Teile des Integumentes nach
einzelnen Klassen, das Visceralskelett des Schädels mit dem Cranialskelett, die Rippen mit der Wirbelsäule,
das innere Ohr mit dem mittleren und dem äusseren usw. beschrieben.

Ferner gehen der vergleichend-anatomischen Beschreibung zwei weitere Kapitel voran. Zuerst gebe ich eine
kurze systematische Übersicht der Wirbeltiere mit Aufzählung hauptsächlich derjenigen Vertreter, welche in dem
Texte erwähnt sind. Diese Behandlungsweise wurde schon von GEGENBAUR in einer etwas anderen Form in
seinem alten Lehrbuche angewendet und ich finde sie vom praktischen Standpunkte aus sehr nützlich.
Sodann folgt eine Beschreibung der ersten Entwicklungsstadien der Wirbeltiere, die für das Verständnis der
in den nachfolgenden Kapiteln zu behandelnden Organogenie unentbehrlich ist. Schließlich wurde dem Bei-
spiele der letzten Auflagen der „Vergleichenden Anatomie“ von WIEDERSHEIM folgend, das Kapitel über die
Beziehung zwischen Eltern und Nachkommenschait eingefügt, diese Frage aber noch ausführlicher als bei
WIEDERSHEIM behandelt. Da die Viviparität (das Lebendiggebären) und die damit verbundene Entwicklung
der Embryonalhüllen nur einen speziellen Fall der Brutpfilege bilden, so mußte in diesem Kapitel auch die bio-
logische Seite der Frage, zu welcher jene Erscheinung gehört, berührt werden.

Bezüglich der Auswahl der Abbildungen muß ich folgendes bemerken: Die neueren Arbeiten geben zwar
ein reiches Material an Wiedergaben von Schnitten, sind jedoch sehr arm an Abbildungen, welche ein Organ
als Ganzes und den Zusammenhang der Organe darstellen; solche Abbildungen sind aber gerade dank ihrer
Übersichtlichkeit und Anschaulichkeit für Unterrichtszwecke die geeignetsten. Natürlich kann man dasselbe
Ziel erreichen, wenn man Abbildungen einer ganzen Serie oder eigene Schemata gibt; im ersteren Fall er-
höhen sich die Kosten der Auflage ausserordentlich, der zweite Weg ist aber für den Verfasser eines Lehr-
buches unangenehm, wenn der Autor der Originalabhandlung selbst ihn zu begehen für nicht möglich hält.

Die Vergleichende Anatomie ist in der Hauptsache eine ideelle und bis zu einem gewissen Grade sogar

eine philosophische Disziplin. Ich würde mich glücklich fühlen, wenn diese Ansicht in dem Leser durch das
Studium meines Lehrbuches nicht zerstört, sondern befestigt würde.

Bitte wenden!

Aus dem Vorwort der Übersetzer: Die Vorzüge, welche das SCHIMKEWITSCH’sche
; „Lehrbuch der Vergleichenden Anatomie der
Wirbeltiere“ vor anderen ähnlichen Lehrbüchern besitzt und welche im Vorwort des Verfassers näher erläutert
sind, haben uns dazu bestimmt, dieses Werk ins Deutsche zu übersetzen. Unsere Beteiligung an der Neu-
bearbeitung der russischen Auflage beschränkte sich unter Anleitung des Verfassers neben einigen Abänderungen

am Texte hauptsächlich auf die Beschaffung von neuen, vielfach farbigen Abbildungen aus Originalabhandlungen
und auf die Herstellung von Zeichnungen nach natürlichen Objekten und Präparaten (meist aus der Sammlung
des Zoologischen Instituts der Universität Tübingen). Unser Bestreben, möglichst alle Abbildungen aus dem
Gebiete der Entwicklungsgeschichte und des Blutkreislaufes, sowie bei Schnitten und schematischen Figuren
in einheitlicher Weise farbig darzustellen, soll den Lernenden das Verständnis der Abbildungen erleichtern, ein
Hilfsmittel, von dem ja bei den Vorlesungen an den Hochschulen schon länger Gebrauch gemacht wird. Auf
diese Weise sind durchweg bei Abbildungen aus der Entwicklungsgeschichte ectodermale Gebilde gelbbraun,
mesodermale karminrot, entodermale grün, ferner beim Blutkreislauf arterielles Blut ziegelrot, venöses blau,
gemischtes violett, schliesslich beim Skelettsystem Knorpel blau usw. angegeben.

—srmH ET

Eee

Bei der Buchhandlung

bestelle ich

Schimkewitsch, Lehrbuch der Ver-
gleichenden Anatomie der Wirbeltiere.

Brosch. M. 18.—
dto. dtoY erh. ae: . Geb. M. 19.50

|

Bitte auszuschneiden und als Drucksache Ihrer Buchhandlung einzusenden.

Ort und Datum Name (bitte recht deutlich)

S————a>c pp di m

Vazl Na exanal analomy 01 Men a

NT- a

There is no BASISPHENOID bone, as just above stated, nor is there an ORBITOSPHENOID.

The ALISPHENOID is bounded by the proötic ventrally, the frontal dorsally and the sphenotie
postero-laterally. Its anterior edge forms the dorsal half of the large orbital opening of the brain
case, this edge of the bone being, because of the flattening of the hind wall of the orbit, presented
almost directly mesially. There is no indication of a parasphenoid leg to the bone. On the dorsal
half of the inner surface of the bone there are two brace-like thickenings, the larger one of which
underlies the antero-lateral corner of the postepiphysial interspace of cartilage, while the other forms
the dorsal end of the anterior wall of the labyrinth recess. The mid-brain recess lies between the two
braces. The anterior edge of the bone is either notched, or perforated by a small foramen which
must transmit the anterior cerebral vein, though this vein was not traced in the dissections. Not
far from the ventral edge of the bone a small opening leads into a canal which traverses the bone and
transmits that branch of the ophthalmicus lateralis that innervates the terminal organ of the supra-
orbital canal.

The SPHENOTIC is bounded by the alisphenoid, proötic and pterotic, and gives support,
on its dorsal surface, to the frontal and postirontal bones. Its dorso-lateral corner comes to the level
of the dorsal surface of the secondary skull, and has surface markings similar to those on the adjacent
dermal bones. Between it and the proötic there is a deep facet for the anterior articular head of the
hyomandibular, while, posteriorly, between the sphenotic and the pterotic, there is a small dilatator
fossa. The bone is traversed by a canal for the ramus oticus facialis, as in Scorpaena.

The DILATATOR OPERCULI, it may here be stated, is found in anterior and posterior
portions which are separated from each other by the complete fusion of a suprapreopercular bone with
the hyomandibular. The anterior portion arises in the dilatator fossa, is fibrous, with but few muscle
fibers, and is inserted on the suprapreopercular and the adjoining portions of the hyomandibular.
The posterior portion is muscular, arises from the posterior surface of the suprapreopereular and the
adjoining portions of the hyomandibular, ventral to the opercular process of that bone, and has its
insertion on the opercular. The fusion of the suprapreopereular with the hyomandibular thus cuts
the originally continuous muscle into two portions.

The PROÖTIGC is bounded by the alisphenoid, sphenotic, pterotic, exoccipital and basioceipital
bones, its ventral edge being overlapped externally by the parasphenoid. The opisthotie does not come
into bounding relations with it. The mesial process of the bone inclines strongly upward and corresponds
to the postpituitary portion, only, of the processes of Trigla and Scorpaena. The lateral corner of
the anterior edge of the process is perforated by the foramen for the nervus abducens. The anterior
edge of the body of the bone is perforated, as in Trigla, by a large opening which is the facialis
opening of the imperfectly enclosed trigemino-facialıs chamber. This chamber forms a deep recess
on the orbital surface of the proötie, and from it four foramina usually lead into the cranial cavity.
Two of these foramina are large, one of them Iying directly dorsal to the other and being separated
from it by a delicate bar of bone. The other two foramina are small, one of them Iying immediately
dorsal to the dorsal one of the two large foramina, and the other one anterior to the line of separation
between the two latter foramina. The dorsal one of the two large foramina transmits the nervus
trigeminus and ramus buccalis lateralis, the ventral one transmitting the nervus facialis. The small
foramen. dorsal to the trigeminus foramen transmits the ramus ophthalmicus lateralis, this foramen

being sometimes fused with the trigeminus foramen. The other smali foramen transmits the eiliaris
Zoologiea. Heft 57. 19

— 146 —

profundi and also the encephalie branch of the jugular vein. The antero-ventral edge of the trigemino-
facialis chamber is either notched, or perforated by a foramen which transmits the palatinus facialıs
{rom the chamber into the myodome, this nerve here, as in Trigla, issuing from the cranial cavity
through the facialis foramen and then running forward along the floor of the trigemino-facialis chamber.
The edge of the orbital portion of the bone, dorsal to its mesial process, is notched to transmit the
oculomotorius, and dorsal to this notch, near the ventral edge of the alisphenoid, there is a second
but shallower notch for the nervus trochlearis.

The MYODOME has proötic and basioceipital portions, and, excepting in that the basi-
sphenoid bone and the prepituitary portions of the mesial processes of the proötics are replaced by
membrane, the canal is the exact equivalent of the canals of Trigla and Scorpaena. There being
no basisphenoid bone, the myodome, in the prepared skull, opens into the hind end of the orbit by
a wide median opening, bounded, on either side, by the ascending process of the parasphenoid. In
the middle line of the floor of the opening there is the median tooth-like process of the parasphenoid.
The hypophysial fenestra extends nearly the full length of the myodome, but is much narrower in
the basioccipital region than in the proötic. The fenestra is completely closed by the underlying
parasphenoid, the myodome not opening, posteriorly, on the ventral surface of the skull. The roof
of the basioceipital portion of the canal is formed by a thin plate of bone, which separates this part
of the myodome from the overlying cavum sinus imparis. The cavum sinus imparis extends poste-
riorly slightly further than the myodome, the pointed ends of both canals being directed toward
the point of the conical vertebra-like depression on the hind end of the basioceipital.

The BASIOCCIPITAL is normal, but presents, in median-vertical section, a marked feature.
The shallow conical vertebra-like depression in the hind end of the bone, in such sections, is lined
by a superficial layer of dense bone differing markedly in appearance from the deeper portions of
the bone. A thinner layer of similar bone lines the deeper conical depression, in the anterior end
of the bone, that forms the hind end of the myodome. The ends of these two cones approach each
other, and the dense bone lining them is continued, in the middle line of the bone, from one cone
to the other. In Scomber I described (’03, p. 102) a similar but much less pronounced line, which,
in that fish, connected the bottom of the cavum sinus imparis with the vertebra-like depression in
the hind end of the basioceipital, and I said that this seemed to indicate that the cavum sinus imparis
might be the remnant of the anterior eonical depression of a vertebral body. In Peristedion it is not
the cavum sinus imparis, but the hind end of the myodome, that has the appearance of being such
a depression on the anterior surface of a vertebral element; and if it be such a depression, it would
offer a rational explanation of the basioceipital extension of the myodome. That this extension
of the myodome is due simply to the fact that the rectus externus, deriving great advantage from
a slight additional posterior shifting of its point of origin, has extensively excavated the basioeccipital,
has never appealed to me. And if a simple posterior extension of its point of origin is of such con-
siderable advantage to the rectus externus, why should it not also be of some advantage to the rectus
internus, which muscle, in Scomber and in all of the mail-cheeked fishes that I have examined,
never acquires this posterior extension? But, if there were a pre-existing depression in the anterior
end of the basioceipital, its occupation and subsequent enlargement by one only of the two muscles
would seem most natural. Similar reasoning, applied to the proötie, would account for the
origin of the proötie part of the myodome, as will be further discussed in the section devoted to the
myodome of fishes. |

— 14 —

The cavum sinus imparis extends, in Peristedion, but slightly beyond the middle of the length
of the basioceipital, the bone posterior to it having a relatively broad, concave dorsal surface, the
posterior portion of which forms the ventral boundary of the foramen magnum and the floor of the
cranial cavity immediately anterior to that foramen. Lateral to the cavum sinus imparis the bone
lodges a small portion of the short subeircular saccular groove.

The basioceipital is, as usual, bounded dorsally, on either side, by the exoceipital, and anteriorly
by the proötic. Ventrally it is overlapped externally by the parasphenoid.

The EXOCCIPITAL is bounded by the basioccipital, proötic, pterotie, opisthotie, epiotie
and supraoceipital, and it is perforated by separate foramina for the glossopharyngeus, vagus and
occipital nerves. The vagus and oceipital foramina have positions similar to those in Trigla, the
vagus foramen, in all my specimens, being divided into two parts by a transverse bar of bone. The
glossopharyngeus foramen lies directly anterior to the vagus foramen, at one half or two thirds the
distance to the anterior edge of the bone. Immediately dorsal to the vagus and glossopharyngeus
foramina there is a slight horizontal ridge along the outer surface of the bone; and dorsal to this
ridge, nearly the entire lateral surface of the brain case is oecupied by a large subtemporal depression
which, as in the other fishes of the group, gives origin to the adductor hyomandibularis and adductor
operculi muscles, and probably also to the fourth and fifth levators of the branchial arches; but the
origins of the levator muscles of the branchial arches were not investigated. The fossa on the proötie,
so well developed in Scorpaena, is apparently represented, in Peristedion, by a slight groove along
the anterior edge of the subtemporal depression.

On the internal surface of the exoceipital there is a mesial process, but it has almost completely
coalesced with the lateral wall of the bone, thus here giving to the bone a thick and distinetly double
ventral edge which suturates with the basioceipital. At the anterior end of this thick ventral edge,
the mesial process separates slightly from the side wall of the bone and so bounds a small dorso-
posterior portion of the saccular groove.

The OPISTHOTIC forms part of the thin ventro-laterally projecting portion of the postero-
lateral edge of the skull. It lies in a nearly transverse position, filling a large and somewhat square
interval between the ventral edge of the posterior process of the pterotic and a right-angled incisure
in that portion of the exoceipital that forms part of the postero-lateral edge of the skull. Because
of its nearly transverse position, the bone forms part of the flat posterior surface of the skull. A
process on its postero-mesial surface gives articulation to the opisthotie process of the suprascapular,
suturating with it. The antero-mesial edge of the bone expands, Y-shaped, and overlaps externally
the adjoining edges of the pterotie, exoccipital, and epiotic, covering also an interval of cartilage
between those bones. The interval of cartilage forms part of the wall of that recess of the cranıal
cavity that lodges the hind end of the sinus posterior utriculi and the related ampulla posterior.
and if the cartilage were to be suppressed the opisthotic would form part of the bounding wall of
the recess.

The EPIOTIC is normal.

The PTEROTIC is bounded, in its deeper, primary portion, by the sphenotie, proötie,
exoccipital and epiotie, the opisthotic overlapping, externally, the ventral edge of that part of the
pterotie that encloses the posterior portion of the external semicireular canal. The dermal portion
of the bone is bounded by the frontal, postirontal, parieto-extrascapular, lateral extrascapular and

— 148 —

suprascapular. The primary portion of the bone encloses, as usual, the outer portion of the horizontal
semicireular canal. On the lateral surface of this part of the bone, near its dorsal edge, is the facet
for the posterior artieular head of the hyomandibular. Dorso-anterior to this facet, a small pit-like
depression forms the posterior half of the dilatator fossa. The posterior process of the bone is relative-
ly small, is directed ventro-laterally and but slightly posteriorly, and is in contact with the dorsal
edge of the opisthotie. The dermal portion of the bone is traversed by the main infraorbital canal,
the section of canal enclosed in the bone lodging one organ innervated by the otiecus, and quite
certainly, though this could not be positively determined, a second, post-preopercular organ innervated
by the supratemporalis lateralis vagi. The primary tubes indicate the presence of two organs here,
one tube arising from the canal at the anterior edge of the bone, another at the hind edge of the bone,
and a third slightly anterior to the middle of the bone; this latter tube issuing from the bone on its
lateral edge, immediately posterior to the facet for the posterior head of thehyomandibular, and anasto-
mosing with the dorsal end of the preopereular canal. The post-preopercular organ must, if present,
be a small one, for it could not be definitely recognized in any of the dissections, although a branch
of the supratemporal branch of the vagus, which nerve contains lateralis fibers, was always found
perforating the pterotic, and going to that part of the canal where the organ would be found,
if present.

On the lateral edge of the pterotic, immediately posterior to the opening of the primary tube
that anastomoses with the preopercular canal, there is a large, slightly convex surface, marked with
striae. This surface lies on a slightly elevated portion of the bone, lies mainly on the primary portion
of the bone, and gives a sliding articulation to the dorsal edges of the united suprapreopercular and
hyomandibular.

The SUPRAOCCIPITAL has dorsal and ventral limbs, the dorsal limb being entirely covered
by the frontals and parieto-extrascapulars, excepting only a small median portion of its hind edge.
The anterior edge of this limb of the bone bounds the hind edge of the postepiphysial cartilage. The
ventral limb of the bone has a prolonged median portion which extends nearly to the dorsal edge
of the foramen magnum. This prolongation of the bone lies upon the external surface of the
adjoining edges of the exoccipitals and on the narrow median band of cartilage that separates those
bones, thus apparently being of ectosteal origin. In its dorsal portion the ventral limb of the bone
expands and is in contact with the exoceipitals and epiotics. In the median line, near the dorsal

end of the limb, there is a small vertical ridge which represents the slightly developed spina
occipitalıs.

2. INFRAORBITAL BONES.

The infraorbitai bones are five in number, all of them traversed by the main infraorbital canal.
The anterior bone, or lachrymal, lodges four sense organs of the line, the second bone one organ,
the third bone two organs, and the fourth and fifth bones one organ each. The total number of organs
enclosed in these bones is thus nine, that being the total number also in both Trigla hirundo and
T. Iyra. The latero-sensory ossicles are not however interfused in the same manner in either of these
ihree fishes, as the following table willshow. The young Trigla lyra, given in this table, is assumed
to have six bones in the series, as Günther says it has, and the arrangement of the organs in this fish
is hypothetical, as all of my fishes had but five bones.

+

— 149 —

Bones T. Iyra (young) T. Iyra (old) Peristedion T.hirundo (young), T. hirundo (old) |
ı Ist. 3 organs Al organs (een organs 3 organs |
| 2nd. ee u | e

| 7 organs
rd. u PH: er ug: | |
| |

th: Ullua2u"r,; | Bea, 2 | | |

a ee Pen a a N 1.3, |

6th. j 1 ’ | 1 PE 1 >>} | 1 „ 1 ”

| |

The lachrymal, in Peristedion, has a long, flat, spatula-shaped anterior portion, which forms
the preorbital process of the skull, and an equally long, but slender and tapering process-like posterior
portion. The spatula-shaped portion projects, its full length, beyond the anterior end of the cranium;
and is marked with surface granulations on both its dorsal and ventral surfaces. It is traversed,
in a somewhat peculiar manner, by the main infraorbital canal. This canal begins at a long groove
on the dorsal surface of the spatula-shaped portion of the bone, the groove beginning at the hind
end of that part of the bone, near its mesial edge, and from there running forward a short distance
parallel to the mesial edge ofthe bone. The hind end of the groove lies immediately antero-mesial to the
antero-lateral corner of the nasal bone, and hence immediately antero-mesial also to the first pore of
the supraorbital canal. The groove is covered, in the recent state, by a drum-head-like membrane
perforated by one or more small pores, and represents the first primary tube of the main infraorbital
canal. From there the canal runs forward to the anterior end of the bone, where it curves latero-
posteriorly and ‘then runs backward to the hind end of the spatula-shaped portion of the bone. There
it leaves the bone, lateral to its posterior, process-like portion, to enter the second bone of the infra-
orbital series. On the ventral surface of the bone, three large oval openings lead into the canal,
each closed by a perforated drum-head-like membrane, these openings representing the 2nd., 3rd.
and 4th. primary tubes of the line. The 5th. tube of the line lies between the lachrymal and the
2nd. infraorbital bone, and it also opens on the ventral surface of the snout; the 6th. tube being the
first one to open on the dorso-lateral surface of the skull. This opening of these first five tubes of
the line, on the ventral surface of a portion of the snout of the fish, associated, as it is, with a
mouth that also lies on the ventral surface of the snout and is supplied with barbels, strongly recalls
the conditions found in Acipenser and Scaphyrhynchus.

The process-like posterior portion of the lachrymal lies along the dorso-mesial edge of the
second infraorbital bone, over-lapping that bone internally. Its pointed posterior end passes beyond
the second bone and there rests upon the external surface of the dorso-mesial edge of the dermo-
ectopterygoid. The base of this posterior portion of the lachrymal is slightly grooved on its mesial
edge and this groove is continued forward along the mesial and anterior edges of a flat depression,
with a curved anterior edge, that lies on the ventral surface of the base of the anterior, spatula-shaped
portion of the bone. The groove and depression lodge the flattened maxillary process of the palatine
and a short adjoining portion of the slender body of that bone, the two bones being firmly bound
together. Posterior to this groove, the lachrymal and palatine are, for a short distance, not in direct
contact, a slit-like opening being left between them; this opening lying opposite the nasal pit and
lodging the lateral portion of the nasal sac. Posterior to this nasal opening the two bones again
come into contact, the rod-like hind end of the palatine lying in a narrow space between the lachrymal

— 150 —

externally and the anterior end of the ectopterygoid internally; the three bones being firmly bound
together. Posterior to the palatine, and in the same narrow space between the lachrymal and
ectopterygoid, a narrow rod of cartilage continues backward and soon expands into a large flat piece
of cartilage which lies against the inner surface of that part of the ectopterygoid that bears the dermo-
ectopterygoid.

The second infraorbital bone is V-shaped, the hollow of the V embracing the bluntly pointed
anterior end of the third bone of the series. The hind end of the dorsal limb of the V ısrounded, and
rests upon the external surface of the dermo-ectopterygoid. The hind end of the ventral Iimb is
slightly grooved on its inner surface, and this groove receives the anterior end of a pointed anterior
process of the quadrate, the two bones being strongly bound together but a slight sliding movement
being permitted. The hind end of the second infraorbital, in some specimens, abuts against, while
in others it does not quite reach, the anterior end of the ventral limb of the preopercular. The main
infraorbital canal enters the bone at its anterior end, and leaves it at the pomt of the angle between
its two limbs, one sense organ being found in the section of canal so enclosed. On the outer surface
of the bone, near the middle of its length, there are two or three spines, these spines lying on the
horizontal ridge already described, and that ridge marking the course of the latero-sensory canal
in the bone.

The third infraorbital bone is large and somewhat parallelogrammic in shape. Its ventral
end is in contact with the dorsal edge of the ventral limb of the second bone of the series, the ventral
half of its anterior edge being in contact with the postero-ventral edge of the dorsal limb of the same
bone. The dorsal half of its anterior edge rests upon the outer surface of the dermo-ectopterygoid,
a small portion of the latter bone coming to the level of the outer surface of the infraorbital bones,
being similarly marked with surface granulations, and appearing as a prolongation of the dorsal
limb of the second infraorbital bone. The hind edge of the third infraorbital bone overlaps internally
and rests against the anterior edge of the ventral half of the preopercular. The anterior portion
of its dorsal edge is thickened, and bevelled on its inner surface, this bevelled surface having a sliding
articulation on that free ventral edge of the ectethmoid that lies posterior to the posterior palatine
articular surface of that bone. The posterior portion of the dorsal edge of the infraorbital bone lies
internal to the fourth infraorbital, the latter bone lying in a large depressed region on the external
surface of the third bone. The bone is traversed by the main infraorbital canal and lodges two sensory
organs of the line.

The fourth infraorbital is a rhoınboidal bone traversed by the main infraorbital canal, and
lodging one organ of that line. It forms almost the entire ventral margin of the orbit, overlaps
externally the third infraorbital, and is bounded both anteriorly and ventrally by that bone. Poste-
riorly, it overlaps externally and rests upon the outer surface of a flange of the hyomandibular, its
hind edge abutting against the anterior edge of the preopercular, and its dorso-posterior corner being
ın contact with the fifth bone of the infraorbital series. On its outer surface there is a low, sharp
and finely serrated longitudinal ridge, which lies superficial to, or slightly dorsal to the enclosed
section of the latero-sensory canal.

The fifth infraorbital is a triangular bone that forms the hind margin of the orbit and transmits
the main infraorbital canal from the fourth infraorbital to the postfrontal, lodging one organ of the
line. Its hind edge rests upon the outer surface of the shank of the hyomandibular, and, in specimens
that have been preserved in alcohol, is so firmly attached to that bone that it appears in process

of ankylosis with it. Ventrally it is in contact with the fourth infraorbital. Posteriorly its ventral
half abuts against the dorsal portion of the anterior edge of the preopercular, its dorsal portion abutting
against the anterior edge of the suprapreopercular bone. The dorsal end of the fifth infraorbital
does not quite reach the lateral end of the postfrontal.

3. SUSPENSORIAL APPARATUS AND MANDIBLE.

The PREOPERCULAR is a large, stout and irregular bone. On its outer surface, slightlv
below its middle point, there is a thin and relatively tall ridge, already referred to, which crosses
the bone horizontally, from one edge to the other, increasing gradually in height from in front back-
ward; and that part of the bone that lies ventral to the ridge inclines ventro-mesially at a marked
angle to the part that lies dorsal to it. The bone is traversed by the preopercular latero-sensory
canal, that canal presenting two straight limbs, a dorsal and a ventral one, which unite at an
angle that lies beneath the horizontal ridge on the outer surface of the bone. The canal lodges six
sense organs.

On the inner surface of the preopereular, following the angular course of the latero-sensory
canal, a flange arises from the bone, the dorsal portion of this flange projecting antero-mesially and
the ventral portion projecting dorsally or dorso-mesially, the two portions of the flange Iying at
the same marked angle to each other that the two limbs of the latero-sensory canal do. In the angle
between the two portions of the flange there is a concave surface which lodges the cartilaginous inter-
space between the hyomandibular and symplectie. Dorsal to this concave surface, in the angular
space between the dorsal limb of the flange and the internal surface of the anterior edge of the bone.
this angle being presented anteriorly, the ventral three-fifths of the hyomandibular is lodged. Against
the lateral, or dorso-lateral surface of the anterior half of the ventral limb of the flange, the broad
flat ventral surface of the posterior process of the quadrate rests; both the quadrate and the hyoman-
dibular being firmly attached to the preopercular.

The HYOMANDIBULAR has, in alcoholie specimens, two dermal bones almost inseparably
fused with its outer surface. The lines of separation between these dermal bones and the underlying
hyomandibular can be everywhere traced, but the two bones could not be removed, without breakage,
in any of the specimens examined, all of which had been preserved in alcohol and then slightly boiled.
One of these two dermal bones is the fifth one of the infraorbital series, and the other the supra-
preopercular. As already stated, the hind edge of the fifth infraorbital bone rests upon the lateral
surface of a flange on the anterior edge of the hyomandibular. This flange arises from a stout longi-
tudinal ridge on the lateral surface of the bone — this ridge being the homologue of the one already
described in the other fishes of the group — and between the flange and the anterior edge of the
body of the bone there is a V-shaped space, the hollow of the V directed anteriorly and forming the
hind end of the flat space included, as in Trigla, between the cheek-bones, externally, and the palato-
quadrate internally. In the hollow of this V, near its ventral end, and hence anterior to the longi-
tudinal ridge on the lateral surface of the bone, the canal for the hyoideo-mandibularis facialis opens,
having traversed the bone from its internal surface. The longitudinal ridge on the lateral surface
of the bone inclines backward, its summit fitting into the V-shaped groove on the anterior edge of
the dorsal limb of the preopereular. The fifth infraorbital was broken and picked off in the specimen
used for the figures.

The SUPRAPREOPERCULAR is in contact, by its ventral edge, with the dorsal end of
the preopercular, and is partly traversed by, and in part forms a bounding wall of the dorsal end
of the preopereular latero-sensory canal; but it lodges no organ of that canal. Its dorsal end lies
immediately behind the posterior articular head of the hyomandibular, and this end of the supra-
preopereular is firmly attached to a flange of bone that fills the obtuse angle between the posterior
articular head of the hyomandibular and its opercular articular head, a circular passage being left
between the two bones to transmit the dorsal end of the preopercular canal. The coinciding dorsal edges
of the suprapreopereular, and the flange of the hyomandibular to which it is attached, form a broad
surface which is slightly concave, is marked with transverse striae, and articulates with the lateral
edge of the pterotic. The articulation is, accordingly, in part with a dermal bone, probably of latero-
sensory origin, and in part with a portion of the hyomandibular that is apparently of membrane
origin. This latter articulation, with a portion of the hyomandibular that is apparently of membrane
origin, is found alone, but much more developed, in Dactylopterus. The intimate attachment of
the suprapreopercular to the hyomandibular has not only completely blocked the passage for the
dilatator operculi muscle, but has cut that muscle into anterior and posterior portions, as already

deseribed.

The anterior and posterior articular heads of the hyomandibular lie close together, on the
dorsal end of the bone, separated by a narrow roughened surface that has the appearance of dermal
bone. The opercular articular head is long and slender, and is connected, by a wide web of bone,
with the ventral portion ofthe shank. The bone is traversed by the canal for the hyoideo-mandibularis
facialis, a single small branch canal transmitting a nerve destined to innervate, as in the other fishes
described, certain organs in the preopereular.

The SYMPLECTIC is a slender bone, with a flattened distal end which lies in the symplectie
groove on the inner surface of the quadrate. Between this flattened distal portion and the proximal
end of the bone, the symplectie arches slightly, leaving a long but narrow space between itself and
the preopereular, this space transmitting the ramus mandibularis externus facialis and the arteria
hyoidea. The mandibularis internus facialis passes anterior to the symplectie, between that bone
and the hind edge of the quadrate, as in the other fishes of the group.

The hyomandibulo-symplectie interspace of cartilage lies in the little concave surface in the
angle between the dorsal and ventral limbs of the flange on the inner surface of the preopercular,
as already stated, but it occupies only the dorsal portion of the concavity. Ventral to it, the
remainder of the concavity lodges the small interhyal, that element artieulating with the cartilage
in a little facet on its ventro-posterior surface. In the corner between the cartilage, the inner surface
of the preopercular, and the ventro-posterior corner of the hyomandibular, there is a small opening
which transmits the ramus hyoideus facialıs.

The QUADRATE has a well developed posterior process, and on the lateral surface of the
postero-ventral edge of this process there is a wide, flat flange. This flange projects dorso-laterally
at an acute angle to the flat, plate-like body of the bone, and its anterior end is prolonged forward
beyond the anterior edge of the body of the bone as a strong anterior process. The ventro-posterior
surface of the body of the flange fits, in larger part, against the internal surface of the ventro-anterior
end of the preopercular, in the angular groove between the body of the bone and the ventral limb
of the flange on its internal surface; but a small anterior portion of this surface fits against the internal

— 153 —

surface of the third bone of the infraorbital series. The anterior prolongation of the flange rests
upon and is firmly bound to the internal surface of the ventral limb of the second infraorbital bone.
The posterior process of the quadrate occupies the anterior half only of the ventral limb of the angular
groove on the preopercular, and the articular head of the bone projects beyond the anterior end of
the preopereular and is there exposed on the external surface of the apparatus in an angular notch
in the ventro-anterior corner of the preopercular. On the internal surface of the quadrate, there is
a shallow symplectie groove.

The METAPTERYGOID has a long and slender dorso-posterior process, the dorsal end of
which closely approaches and is bound by tissue to a thin web of bone on the anterior edge of the hyo-
mandibular; this process thus being the internal flange on the hind edge of the bone. At the
base of the process there is a slightly developed external flange, the hind edges of both flanges being
widely separated from the anterior edge of the hyomandibular. In the V-shaped space between
the two flanges a portion of the levator areus palatini has its insertion. The ventro-anterior edge
of the bone is everywhere separated from the quadrate by a narrow line of cartilage, the posterior
corner of this edge of the bone being in contact with the symplectic.

The ENTOPTERYGOID is a small, thin plate of bone which lies in the membrane that covers
the ventral surface of the adductor arcus palatini muscle. Its ventral edge rests against the inner
surface of the narrow band of cartilage that lies between the quadrate and metapterygoid, usually
extending forward slightly beyond that cartilage onto the inner surface of the ectopterygoid. Its
hind edge overlaps slightly the inner surface of the metapterygoid.

The ECTOPTERYGOID is a stout bone, with the usual dorsal and ventral limbs lying at an
angle to each other. The two limbs of the bone form a thin plate, which is completely ankylosed,
at the angle between the two limbs, with a plate of bone which is certainly of separate origin, and
which has been already referred to as the dermo-ectopterygoid. The ventral limb of the bone has
the usual position along the internal surface of the anterior edge of the quadrate, the dorsal limb
lying along the ventral and outer surfaces of the hind end of the palatine, and also along the same
surfaces of the palatine cartilage.

The DERMO-ECTOPTERYGOID lies on the external surface of the thin plate formed by
the two limbs of the membrane-ectopterygoid, and extends from the angle between the two limbs
of that bone forward along the dorsal limb. It projects dorsally beyond the membrane-ectopterygoid,
along the lateral surface of the enlarged posterior portion of the palatine cartilage, and then beyond
that cartilage, there forming an important angle in the apparatus. The ectal surface of the bone
is presented dorso-laterally, and the posterior half of this surface lies against and is firmly bound
to the inner surface of the antero-dorsal corner of the third infraorbital bone. A small anterior portion
of the plate lies against but is much less firmly bound to the inner surface of the hind end of the
dorsal limb of the second infraorbital bone. Between these two surfaces of contact with the infraorbital
bones, the outer surface of the plate is granulated and comes to the level of and forms part of the
outer surface of the bony euirass of the cheek. The dorsal edge of the plate is presented dorso-mesially,
and its thick posterior portion is grooved, the groove artieulating with the artieular ridge near the
hind end of the lateral edge of the ectethmoid. Anterior to this groove the dorsal edge of the plate
is thin, and lies against the lateral surface of the rod of palatine cartilage, the latter cartilage not

coming into articular relations with the ectethmoid. On this thin portion of the dorsal edge of the
Zoologiea. Heft 57. 20

— 154 —

bone, and also on the mesial edge of the grooved portion posterior to it, rests the slender pointed
hind end of the posterior, process-like portion of the lachrymal. This end of the lachrymal is grooved
on its dorso-external surface, and participates in the articulation with the ectethmoid, the articulation
thus representing the lachrymo-ethmoid artieulation of the other fishes described. The dermo-
ectopterygoid, completely ankylosed with the ectopterygoid, thus fulfils the function of the posterior
ethmoid process of the palatine of both Scorpaena and Trigla; but nevertheless the bone does not
seem to be a palatine element, its relations to the ectopterygoid being much more intimate than
those to the palatine.

The PALATINE is a slender rod of bone with an enlarged and flattened anterior end. The
ventral surface of the hind end of the rod-like portion of the bone rests against the dorso-mesial
surface of the dermo-ectopterygoid, as just above described. The lateral surface of this end of the
palatine, or the lateral surface of the covering dermo-ectopterygoid, and the lateral surface also of the
anterior portion of the palatine, rest against the internal surface of the posterior, process-like portion
of the lachrymal, the slit-like opening between these two surfaces of contact lodging the lateral portion
of the nasal sac. In the angle between the rod-like part of the bone and its enlarged anterior end,
on the mesial surface of the bone, there is a concave articular surface, with a slight process at its
anterior edge. This articular surface hooks around and articulates with the anterior edge of the
little anterior palatine eminence of the ethmoid cartilage. Anterior to this articular surface, the
anterior end of the palatine widens, its mesial edge being slightly concave and its anterior edge
rounded and capped with cartilage. This part of the palatine forms its maxillary process, and fits
in the depression and groove, already described, on the ventral surface of the base of the spatula-
like anterior portion of the lachrymal. Between the curved mesial edge of this maxillary process
of the bone and the lateral portion of the anterior edge of the vomer, a semi-oval space is enclosed,
through which the ascending process of the maxillary projeets from below upward; this process of
the maxillary artieulating by one surface with the vomer and by the other with the palatine, and
being bound to both bones by connective tissue.

The OPERCULAR has the irregular shape shown in the figures. On the inner surface of the
anterior edge of the bone there is a deep depression which receives the opercular articular process
of the hyomandibular. Dorso-posterior to this depression there is a larger depression on the inner
surface of a dorsal, process-like portion of the bone, this depression giving insertion to the adductor
operceuli. Dorsal to the surface of insertion of this latter muscle, in a narrow line along the dorsal
edge of the bone, the levator operculi has its insertion. The dilatator operculi is inserted on the
anterior edge of the bone, immediately lateral to the artieular facet for the hyomandibular. On the
outer surface of the bone there is a horizontal ridge which terminates posteriorly in a spine, this spine

being double in one of my specimiens. Dorsal to this spine there is, on the hind edge of the bone,
a second spine.

The SUBOPERCULAR is a delicate bone that lies along the inner surface of the hind edge
of the opercular, projecting dorsally beyond the dorsal edge of that bone.

The INTEROPERCULAR lies along the inner surface of the preopereular, considerably anterior
to, and wholly detached from the opercular and subopereular. Its antero-ventral end is slender and
rod-like, and almost reaches, and is bound by ligament to, the hind end of the mandible. Its dorso-
posterior portion is flat and kroad, and lies against and is firmly bound by ligament to the lateral

— 15 —

surface of the proximal end of the ceratohyal, near the point where that bone artieulates with the
interhyal; the attachment apparentlv being to the interhyal as well as to the ceratohyal. From
the dorso-posterior end of the interopereular a stout ligament arises, and running dorsally, parallel
to and immediately posterior to the interhyal, is inserted on the inner surface of the preopereular.

‚The MANDIBLE is strongly curved at its anterior end, to meet, in the middle line, its fellow
of the opposite side. Its middle point lies considerably posterior to the corresponding point of the
upper jaw, and the dentary, like the maxillary, the premaxillary, and the vomer is wholly without
teeth. The articular has a pointed anterior end which projects slightly beyond the hollow of the
V between the dorsal and ventral limbs of the dentary, and there lies internal to that bone. Posterior
to this point, the ventral edge of this portion of the articular slightly overlaps, externally, the dorsal
edge of the ventral limb of the dentary. On the internal surface of the bone, posterior to the hind
end of Meckel’s cartilage, there is a slight eminence for the insertion of the tendon of a part of the
adductor mandibulae muscle. The bone has a broad thin coronoid process. The angular is almost
completely fused with the articular, a sutural line on the external surface of the bone alone indicating
its presence. The dentary has a long and slender dorsal limb which does not reach, by a considerable
interval, the dorsal end of the coronoid process. On the lateral surface of the dorsal edge of the
dentary, slightly anterior to the middle of its length, there is a dorso-laterally projecting shelf of bone;
and immediately beneath this shelf, on the external surface of the bone, there is the large anterior
opening of a short canal which leads backward through the dentary into the ramus of the mandible.
This canal transmits a large nerve which goes immediately to the large barbel of the fish, this barbel
having its attachment on the outer surface of the dentary in a pit-like depression that lies immediately
ventral to the anterior end of the projecting shelf of bone. On the projecting antero-lateral corner
of this shelf of bone the mandibular labial fold has its origin. The barbel of Peristedion thus arises
from the mandible in the place where the gristle-like core of the mandibular fold of Scorpaena arises,
and, contiguous with it, the mandibular fold has its origin. Whether this means that the core of the
mandibular fold of Scorpaena represents, or includes, the barbel of Peristedion, or not, I can not
determine.

The dentary and articular are both traversed by the mandibular latero-sensory canal, the
dentary lodging three sense organs of the line, and the articular one organ.

4. LATERO-SENSORY CANALS.

The main infraorbital canal has the course already described throush the infraorbital bones,
the lachrymal lodging four organs of the line, the second infraorbital bone one organ, the third bone
two organs, and the fourth and fifth bones one organ each; making nine organs in all in this part
of the line, that being the same number as in Trigla. The canal then traverses the postirontal, in
which bone there is a single organ innervated by a branch of the oticus lateralis, and then anastomes
with the penultimate tube of the supraorbital canal. The canal then traverses the pterotie, in which
bone there is a large pre-preopereular organ innervated by a branch of the oticus lateralis, and in
all probability a second and much smaller post-preopercular organ innervated by a branch of the
supratemporalis lateralis vagi. A branch of the latter nerve was found going to the canal in four
different specimens, butthe organ, if it exists, is so small that it could not be with certainty identified.
The canal anastomoses with the dorsal end of the preopercular canal between these two organs.

— 1567 —

Having leit the pterotie, the canal traverses a groove in the lateral edge of the lateral extrascapular,
but no organ could be found related to that bone. The canal then traverses in succession the supra-
scapular and supraclavicular, in each of which bones there is a single organ.

The main infraorbital canal of Peristedion thus differs from that of Trigla in that the pterotie
lodges but one organ innervated by the oticus lateralis, instead of two, without intervening primary
tube; and in that there is no apparent organ related to the lateral extrascapular.

The supratemporal canal lodges, as in all the other fishes of the group, two organs, one lying
in the lateral extrascapular and the other in the parieto-extrascapular.

The supraorbital canal agrees strietly with the canal in Scorpaena and Trigla, but between
the nasal and frontal bones the canal is enclosed, for a relatively long distance, in the dermal portion
of the mesethmoid bone; this section of canal lodging no sense organ. The nasal lodges a single sense
organ, and the frontal five organs, the fourth and fifth organs of the line lying close together without
intervening primary tube, as in Scorpaena and Trigla. The fourth primary tubes of opposite sides
unite in the middle line to form a frontal commissure.

The preoperculo-mandibular canal contains ten organs, instead of eleven as in Trigla, three
of these organs lying in the dentary, one in the articular and six in the preopercular. After leaving
the dorsal end of the preopercular the canal traverses a short suprapreopercular bone, without related
organ, to reach and anastomose with the main infraorbital canal between the two organs in the pterotie.

The primary tubes, in Peristedion, do not branch repeatedly after entering the dermal tissues,
as they do in Scorpaena, Cottus and Trigla. Certain of the tubes, however, apparently undergo one
or two subdivisions, and the mouths of all of them become enlarged and most of them are closed
by drum-head-like membranes perforated by several small openings.

IV. Dactylopterus volitans.

h 1. SKULL.

Of this fish I have had five specimens, ranging from 13 cm to 41 cm in length, and a number
of specimens ranging from 5 cm to 10 cm in length. A single one of these specimens, 35 cm in
length, was the only one I had during the earlier periods of the investigation, the other large specimens
being later obtained, one at a time. The study of the cranial bones presenting peculiar diffieulties,
all of these large specimens were successively sacrificed to it, the soft parts thus not being examined
in any ofthe adults. When the small specimens were later obtained, several of them were sectioned,
but, because of the character of the bones and other tissues, only one comparatively good series of
sections was obtained. This series alone served for the study of the nerves.

. Gıll (90, p. 245) says, of the skull of Dactylopterus, that „its upper surface is dere partly
irom a dermal ossification which is incongruous with the true bones“. Just what this statement
means is not clear, for the bones in this fish differ in no way, excepting in degree, from those in Trigla
and Peristedion. As in these two latter fishes, all of the primary bones that come to the level of,
and form part of the dorsal surface of the skull of Dactylopterus have an external surface exactly
similar to that of the adjoiming and purely dermal bones; and the sections of young Dactylopterus

157 —

show, better even than those of the other fishes of the group, that this external portion of these
primary bones is formed by osseous accretions that are apparently developed in exactly the same
way as the corresponding portions of the purely dermal bones. A 13 cm specimen was treated with
chlorine, in an early attempt-to trace the sutures between the cranial bones, and ın this preparation
a superficial layer of bone could be stripped off from both the purely dermal and the primary bones,
leaving, in the former case, a thin remaining plate of bone which may perhaps represent a separate,
membrane component underlying a more important dermal or latero-sensory component. This
membrane component would then be the part that persists in those higher animals in which the
latero-sensory component has disappeared.

The skull of Daetylopterus is said by Cuvier & Valenciennes (’29, vol. 4, p. 131) to be depressed
and widened in such a manner that it represents a subrectangular disk, the anterior edge of which
is curved in an obtuse angle, and its posterior angles prolonged into long points. A very large median
ethmoid and two prefrontals are said to form an anterior row of the bones that form the pavement-
like dorsal surface of the skull. A second row is said to be formed by the large frontals, behind each
of which bones there is a small postfrontal. A third row is formed by the median interparietal, the
two parietals, and the two mastoids; and a fourth row by the two external oceipitals and two
suprascapulars. Between the third and fourth rows, on either side, two oval bones are said to be
intercalated, these two bones together, on each side, representing the „rocher“.-

The prefrontals of this terminology are the ectethmoids of the nomenclature employed by
me, the interparietal is the supraoccipital, and the mastoid is the pterotic. The term „‚rocher“, as
used by earlier authors, is said by Starks (’01) to be the synonym of the opisthotic of later authors;
but it-will be shown-that‘the so-called „rocher‘‘ of Dactylopterus is the lateral extrascapular, and
not the opisthotie of the fish, this latter bone being wholly absent. It will be further shown that
the external occipital is a mesial extrascapular, and not an epiotie; and, what is much more important,
it will be shown that the median ethmoid is not an ethmoid bone at all, but is a median bone formed
by the fusion, in the middle line, of the two nasals.

Gill (°88) calls the median ethmoid of Cuvier and Valenciennes the prosethmoid, and says
that it and the anteal (vomer) are „‚entirely disconnected, leaving a capacious rostral chamber opening
backwards mesially into the interorbital region‘. Into this rostral chamber the well developed ascend-
ing pedicles of the intermaxillines (premaxillaries) are said to glide. And as Gill, in his descriptions
of the Loricati, says that the ascending pedicles of the intermaxillines glide „‚over the front of the
prosethmoid“, the term prosethmoid, as used in his deseriptions of Dactylopterus, is certainly intended
by him to designate a bone that he considered as the striet homologue of the median, primary
mesethmoid of current descriptions. No mention is made of a rostral either by Gill or by Cuvier
and Valenciennes.

The floor of the rostral chamber, in my medium-sized specimens, inclines downward and
forward at an angle of about 45°. In the 41 cm and 35 cm specimens this floor is somewhat less steep,
while in the small specimens it is much steeper. In the middle line of the anterior half of the floor,
there is a narrow strip of cartilage formed by a median rod-like projection from the anterior end
of the antorbital cartilage. This rod-like process is the striet homologue of the prenasal process,
or beak, of my descriptions of Amia and Scomber, but it is here a relatively long and narrow rod,
curving downward and forward. It lies in a median groove on the dorsal surface of the vomer, and
extends to the anterior edge of that bone, agreeing in this with the arrangement found in Scomber.

— 158 —

On either side of this median rod of cartilage, the dorsal surface of the vomer forms the floor of the
anterior half of the rostral chamber. Posterior to the vomer, the antorbital cartilage expands rapidly,
on either side, and, then again contracts to a narrow median column which is continuous dorsally
with the ventral surface of the anterior end of a broad band of cartilage which forms the roof of the
interorbital, olfactory prolongation of the cranial cavity. A diamond-shaped or nearly square surface
of cartilage thus forms the median portion of the post-vomerine portion of the floor of the rostral
chamber, this cartilage being bounded laterally, on either side, by the pedicle of the ectethmoid.
There is thus no bone whatever at any point in the median line of the floor of the chamber.

The hind wall of the rostral chamber is formed by the median column of cartilage just above
referred to, and, dorsal to that column, by the broad anterior end of the roofing band of interorbital
cartilage. This anterior end of this latter cartilage projects forward slightly beyond the median
column, slightly overhangs the hind end of the rostral chamber, and gives support, on its dorsal
surface, to the hind end of the so-called median ethmoid. Immediately beneath this part of the
median ethmoid there is, on either side, a slight eminence on the anterior edge of the cartilage, each
eminence giving origin to a ligament which runs antero-ventrally and is inserted on the dorsal surface
of the maxillary immediately lateral to its ascending process. This ligament is thus the homologue
of the ethmo-maxillary ligament of the other fishes of the group, and the little eminence of cartilage
{rom which it has its origin must accordingly be the mesethmoid process; but it is a process of the
ethmoid cartilage only, there being no primary bone whatever in any immediate relation to it. On
a slight median ridge in the cartilaginous floor of the chamber, the ventral surface of the rostral glides.
There is accordingly, in this fish, no mesethmoid bone. That the median portion of the ethmoid
cartilage should remain unossified, and that a median ethmoid bone, of primary origin, should
nevertheless be found wholly external to that cartilage, dorsal to the rostral instead of ventral to it,
and dorsal even to the mesethmoid processes of the ethmoid cartilage, is evidently impossible.

The roof of the rostral chamber is formed by the single median so-called ethmoid or proseth-
moid. This bone suturates posteriorly with the frontals. Laterally, on either side, it’ suturates,
in its posterior half, with the ectethmoid, while in its anterior half it forms the mesial boundary of an
elongated nasal opening; which opening lies between this so-called ethmoid and the anterior portion
of the eetethmoid, opens direetly into the nasal pit and encloses the two nasal apertures. At the
anterior end of the opening, the two bounding bones closely approach each other, but do not quite
come into contact, a narrow space being left between them, closed antero-ventrally by the lachrymal.

Slightly antero-mesial to the nasal opening, there is, on the anterior edge of the so-called
ethmoid, a short, broad, stout process which projects ventrally and antero-laterally. This process
arises from the deeper layers only of the bone, the anterior edge of that superficial portion of the
bone that bears the surface markings continuing, uninterruptedly, external to it. The internal surface
of the process forms a large flat articular surface which gives a sliding artieulation to the flattened
anterior end of the maxillary process of the palatine. On its external surface the process gives support
to the internal surface of the dorsal edge of the lachrymal, the two bones being strongly but somewhat
loosely bound together by fibrous tissue, a slicht sliding and oscillating motion, combined, of the
lachrymal being permitted. The process thus corresponds, in its relations to the palatine and lachry-
mal bones, to the process-like antero-lateral corner of the nasal bones of Trigla and Peristedion,
excepting that here, in Dactylopterus, it is developed as a process-like prolongation of the ventral
layers of the bone, and is interposed between the palatine and lachrymal instead of Iying on the

— 19 —

dorsal surfaces of those two bones. The process may accordingly be called the lachrymo-palatine
process of the bone. From its postero-lateral edge, on the internal surface of the body of the bone,
a tall sharp ridge begins, and running postero-mesially, nearly to the hind end of the bone, marks the
boundary between the dorsal portions of the rostral chamber and the nasal pit; those two chambers
being confluent beneath the ridge. Between the hind ends of the ridges of opposite sides there is,
on the internal surface of the bone, a deep median pit which nearly perforates the bone and lodges
the distal ends of the ascending processes of the premaxillaries. Immediately postero-lateral to the
lachrymo-palatine process, close to the narrow space that leads into the nasal opening, the supra-
orbital latero-sensory canal begins, and running at first dorso-mesially and then curving posteriorly,
traverses the bone and issues at its hind edge, there entering the frontal. This median so-called
ethmoid or prosethmoid bone of Dactylopterus is thus certainly a bone formed by the fusion, in the
mediıan line, of the two nasal bones of the fish.

The ROSTRAL is a narrow, flat and tall cartilage, which lies between the hind ends of the
articular processes of the premaxillaries, and gives support, on its dorsal edge, to the ascending
processes of those same bones. Its ventral edge has a slight median groove, and this groove slides
upon a slight median ridge on the cartilaginous floor of the rostral chamber. The rostral is relatively
small, as are also the maxillary and premaxillary bones; and all of these elements of the upper jaw
of the fish are entirely concealed, in dorsal and lateral views, beneath the nasal and lachrymal bones.

The PREMAXILLARY has a long, flat and pointed ascending process, a relatively long,
large and flat articular process, and a short and flat horizontal portion, or body. The short body
of the bone ends in a broad blunt end, and its flat oral surface is garnished its full length, or very
nearly so, with small villiform teeth. The ascending process arises by a broad base from the mesial
(proximal) end of the body of the bone, and, in the medium-sized specimens, is directed dorsally
and but slightly backward. It lies in a nearly longitudinal plane, inclining and but slightly ventro-
mesially, the flat surfaces of the processes of opposite sides enclosing between them a deep and
narrow groove. The long flat articular process also lies in a nearly longitudinal plane, inclined at a
slight angle to the ascending process, the two processes projecting dorso-posteriorly nearly parallel
to each other and separated by a narrow intervening space. From the distal surface of the base
of the ascending process a rod of tough gristly tissue arises, and extending distally along the dorsal
surface of the body of the bone, is attached, at its distal end, to the distal end of the maxillary.
This rod of gristly tissue lies in the upper labial, or maxillary dermal fold, thus occupying a position
that corresponds to that occupied by a considerable part of the body of the premaxillary in the other
fishes of the group, the actual body of the premaxillary of Dactylopterus corresponding, not to
the premaxillaries of the other mail-cheeked fishes, but, approximately, to the premaxillaries of

®those fishes in which the maxillary is said by Sagemehl to lie lateral (distal) to the premaxillary.

The MAXILLARY has a relatively large, right-angled ascending process, similar to that
of Scorpaena, and a short broad ligamentary process which corresponds to the proximal half only
of the process of Scorpaena. The distal end of the short and slender body of the bone is slightly
expanded, gives attachment to the hind end of the upper labial rod of gristly tissue, and lies in a
marked depression on the outer surface of the mandible. The bone articulates with the premaxillary
and vomer in the same way that it does in Scorpaena, and it gives articulation, on the dorsal surface
of its ligamentary process and the adjacent portions of its body and ascending process, to the anterior

— 160 —

end of the maxillary process of the palatine. It does not give support, at any point, to the lachrymal;
but a short, strong ligament extends from the summit of the ascending process of the bone to the
dorsal edge of the lachrymal, this ligament having its attachment also in part on the lJachrymo-palatine
process of the nasal.

The LIGAMENTS associated with the upper jaw were not properly investigated, the smaller
specimens not being suitable for this investigation, and the skeletons of the larger specimens having
been prepared, as already stated, without special attention being given to any of the soft parts. The
ethmo-maxillary ligament is well developed, even in the small adults, and has already been described.
The rostro-palatine ligament is also well-developed and has the usual relations, but, because of the
shortening and deepening of the snout, it lies in a nearly horizontal position, the position being the
more nearly horizontal, the smaller the specimen. The tendon of that part of the adductor mandibulae
muscle that has its insertion on the maxillary in the other fishes of the group, is here also well devel-
oped, and, the posterior portion of the ligamentary process of the maxillary not being developed,
is inserted on the dorsal surface of the body of the bone near its proximal end. The naso-maxillary
ligament is a short stout ligament that extends from the lachrymo-palatine process of the nasal to the
outer end of the ascending process of the maxillary. The vomero-palatine and lachrymo-palatine
ligaments are reduced, because of the articulating contact of the parts concerned, to tough fibrous
or ligamentous tissues that hold the articulating surfaces together. No other definite ligaments
were recognised in the dissections, but in the sections of the small specimens there is a well developed
ligament that extends from the lateral surface of the rostral to the dorsal end of the ascending process
of the maxillary; and another that extends from the ventral (here posterior) edge of the ascending
process of the premaxillary to the proximal end of the maxillary, this ligament traversing the narrow
space between the rostral and the articular process of the premaxillary.

The VOMER differs somewhat from the bone in the other fishes of the group, and it can
be best understood by stating, at once, that this part of the skull of Dactylopterus has been so greatly
flattened that the ascending processes of the vomer have apparently been pressed down upon and
become completely fused with the underlying body and lateral processes of the bone; the antorbital
cartilage being, so to speak, squeezed out from between the dorsal and ventral limbs of the bone.
As a result of this, the vomer is a solid bone of the shape shown in the figures, with a convex ventral
and a concave dorsal surface, the exposed portion of the latter surface being about two-thirds as
long as the ventral surface of the bone, and representing the ascending processes of the bone. This
part of the dorsal surface of the bone forms the floor of the anterior portion of the rostral chamber,
is grooved in the middle line to receive the rod-like prenasal process of the antorbital cartilage, and,
lateral to that groove, on either side, has a slightly raised and flattened surface which gives articulation
to the ascending process of the corresponding maxillary. The middle portion of the hind edge
of this part of the vomer abuts against the anterior edge of the antorbital cartilage, but whether
it is in synchondrosis with that cartilage or not, could not be definitely determined. Apparently
it is not, the vomer of Dactylopterus seeming to be a purely dermo-membrane bone, and not apprec-
iably overlapping or having perichondrial relations to the dorsal surface of the adjacent cartilage.
Lateral to the antorbital cartilage, on either side, the thin hind edge of this part of the vomer — here
apparently formed by the fusion of the lateral and ascending processes — suturates with the pedicle
of the corresponding ectethmoid, the hind end of the short body of the bone underlying the antorbital
cartilage and suturating with the parasphenoid.

= el

The head of the vomer is bent downward and thickened, as in the other fishes of the group,
this thickened portion forming a broad transverse but untoothed surface which extends across the
anterior end of the ventral surface of the bone. The lateral ends of this dental but untoothed ridge
are concave or flattened, and give origin, on either side, to a very short but stout vomero-palatine
ligament which has its insertion on the internal surface of the anterior end of the body of the palatine.
Beginning immediately lateral to the dental ridge, at the anterior edge of the vomer, a slight ledge
extends postero-laterally across the ventral surface of the bone to its hind edge, and that small part
of the ventral surface of the bone that lies antero-lateral to this ledge lies at a slightly deeper level
than the remainder of the surface. The anterior edge of this little surface of the bone is rounded,
fits into a deep groove on the internal surface of the base of the maxillary process of the palatine,
and gives articulation to that bone; the tall posterior wall of the groove on the palatine fitting against
the little depressed surface on the vomer and the edge of this part of the groove abutting against
the ledge on the vomer and so limiting the inward swing of the palato-quadrate apparatus. The
rounded artieular edge of the vomer is continuous with a similar edge on the pedicle of the ectethmoid,
the latter bone apparently participating slightly in the articulation; this artieulation thus certainly
containing the anterior ethmo-palatine articulation of the other fishes of the group, and apparently
representing that articulation alone. Posterior to the articular groove on the palatine, the dorsal
edge of the latter bone abuts against the ventral surface of the pedicle of the eetethmoid and is bound
to it by tough fibrous tissue, this contact apparently representing the posterior ethmo-palatine artic-
ulation, here practically suppressed.

The ECTETHMOID has a somewhat diamond-shaped and strongly convex external surface,
the dorsal and lateral surfaces of the bone being inclined at more than a right angle to each other,
and the lateral edge of the bone being, in consequence, directed. ventro-mesio-posteriorly. The
posterior edge of the bone is eurved and slightly concave, is presented postero-laterally, and forms
the anterior portion of the margin of the orbit. The mesial edge of the bone forms two sides of the
diamond-shaped outline of the bone. The posterior one of these two sides is straight, is presented
postero-mesially and suturates with the frontal; the anterior one suturating in its posterior half
with the nasal, while its anterior half is occupied by a deep, oblong ineisure which forms the ventro-
antero-lateral boundary, and part of the dorso-postero-mesial boundary of the nasal opening. The
bent-under lateral edge of the bone is slightly concave, the concavity arching over the lateral edge
of a tall and flat articular eminence which begins at this edge of the ectethmoid and extends mesially
and slightly posteriorly along the ventral surface of the bone. This eminence projeets ventro-mesially
and gives articulation to a facet on the dorsal edge of the lachrymal.

Beneath the eurved external, and evidently purely dermal portion of the eetethmoid, the
deeper portion of the bone extends into the cartilage of the antorbital process, forming a sort of
pedicle to the external portion. The pedicle is directed ventro-mesially, and is partly in synchondrosis
with the median remnant of the antorbital cartilage, and partly in sutural contact with the vomer
and parasphenoid. The anterior surface of the pedicle is deeply hollowed to form part of the bounding
wall of the nasal pit, its posterior surface being less deeply hollowed to form part of the anterior wall
of the orbit. In the mesial edge of the pedicle there is an ineisure which, with the adjoining cartilage,
forms a foramen which transmits the olfactory nerve from the orbit to the nasal pit.

The ORBIT is deep and low, with curved but nearly transverse anterior and posterior walls,

formed, as usual, by the concave posterior surface of the ectethmoid and the anterior surface of the
Zoologica. Heft 57. D31

brain case. The latter surface inclines slightly forward, but lies, as just above stated, in a nearly
transverse position. It is formed, as usual, by the proötie, alisphenoid and sphenotie, but the latter
bone is reduced and forms only the small dorso-lateral corner of the wall. The wide roof of the orbit
is formed mainly by the frontal but partly also by the ectethmoid and sphenotie. Its floor is formed
in part by the expanded base of the pedicle of the ectethmoid, in part by the wide parasphenoid,
and in part also by the large orbital shelf of the second bone of the infraorbital series.

The interorbital wall is relatively thick. It is single in its ventral but double in its dorsal
portion, this latter portion enclosing an anterior prolongation of the cranial cavity, which extends
the full length of the interorbital region and lodges the olfactory nerves. The anterior half, approx-
imately, ofthe wall is cartilaginous, and here the olfactory prolongation of the eranial cavity is roofed
by a wide flat band of cartilage, already referred to when describing the rostral chamber. The
posterior half of the wall is formed, in its ventral portion, by a median interorbital process of the
parasphenoid, and in its dorsal portion by the alisphenoid of either side, the expanded dorsal edges
of the latter bones not quite touching in the median line and so leaving a narrow longitudinal opening
in the roof of this part of the olfactory extension of the cranial cavity. A ventral flange to the frontal,
found more or less developed in all the other fishes of the group is here wholly wanting.

The cartilaginous portion of the interorbital wall is perforated, close to its antero-dorsal corner,
by a large oval opening which leads from orbit to orbit and is closed, in the recent state, by membrane.
This membrane is single in its ventral but double in its dorsal portion, the latter portion enclosing
the anterior end of the olfactory prolongation of the cranial cavity, which prolongation extends
to the hind surface of the short pillar of cartilage that forms the hind wall of the rostral chamber.
The membrane is pierced, on either side, by the olfactory nerve, that nerve then traversing the
extreme anterior end of the orbit to enter and traverse the opening that leads from the orbit into
the nasal pit, that pit being, as already stated, confluent with the rostral chamber. From the single,
ventral portion of themembrane, ventral to the olfactory nerves, the obliqui muscles have their origins.

The median interorbital process of the parasphenoid, above referred to, is a tall broad Y-
shaped process, the spreading arms of which may be said to present three regions. In the anterior
region each arm is formed by a thin plate of bone which overlaps externally the anterior edge of
the corresponding alisphenoid, and, anterior to that bone, lies against the external surface of a part
of the cartilage that encloses the interorbital extension of the cranial cavity. In the middle region,
the dorsal edge of either arm is thickened and suturates with the ventral edge of the corresponding
alisphenoid. In this region the dorsal surface of the process seems to form the floor of the interorbital
extension of the cranial cavity, but there may here have been delicate lining plates of cartilage that
were lost in dissection. The basal portions of the arms of the Y are connected, at the hind edge of
this middle region, by a delicate transverse web of bone. In the posterior region, the arms of the Y
are short and spread considerably, thus forming, on the dorsal edge of this part of the process, a
basin-like depression in which the optic chiasma rests. The alisphenoid of either side arches above
this optie depression of the process of the parasphenoid and, anterior to it, suturates, as already
stated, with the corresponding dorsal edge of the olfactory portion of the process. The posterior
corner of each arm of the Y is prolonged and terminates in a point direceted toward, or even reaching
the dorsal edge of the orbital surface of the proötic. A large fenestration of the interorbital wall is
thus here formed which may be wholly enclosed by the bounding bones, those bones being the alı-
sphenoids and proöties of either side and the median interorbital process of the parasphenoid. The

— 163 —

fenestration, in the prepared skull, leads from orbit to orbit, traversing the interorbital portion of
the cranial cavity. In the recent state, the fenestra of either side is closed by a membrane which
is pierced by the optic nerve as it passes from the cranial cavity to the orbit. The two fenestrae
are accordingly the optic fenestrae.

The interorbital process of the parasphenoid of Dactylopterus would seem to be the homologue
of the median process of the same bone of Gymnarchus, as shown in Erdl‘s (47) figures, which
process is considered by that author as the lower portion of the ala magna, and by Ridewood (’04b,
p. 198) as the basisphenoid. It seems also to be the equivalent of the basisphenoid of Ameiurus
(‘Me Murrich, ’84), fused, perhaps, with the orbitosphenoid of that fish. It is apparently the homo-
logue of the median process of the parasphenoid of Peristedion, but enormously developed. That
it contains an originally independent basisphenoid element, as its general relations would certainly
indicate, seems improbable, for even in 5 cm specimens there is no slightest indication of two inde-
pendent ossifications. In these latter specimens, the process is apparently wholly of membrane
bone, but it is in part formed by two thin laminae of bone which enclose between them a part of
the cartilage of the interorbital septum, much as the pedicle of the basisphenoid does in young
specimens of Scorpaena.

Ventral to the optice fenestra, and, in most of my specimens, partly confluent with it, there
is a second large perforation of the posterior portion of the interorbital wall, this perforation also
leading from orbit to orbit but not traversing any portion of the cranial cavity. This perforation
is bounded anteriorly by the hind edge of the interorbital process of the parasphenoid. Ventro-posteri-
orly it is bounded by a tall and thin ridge of bone which extends transversely across the dorsal sur-
face of the parasphenoid between the small and pointed ascending processes of that bone. Thisg
ridge of bone projects dorso-posteriorly, suturates on either side with the anterior edge of the ventral
portion of the proötie and slightly also with the ventral edge of the orbital portion of that bone, but
between the two proötics presents a free dorsal edge. In the recent state, a membrane extends from
this free portion of the edge of the ridge upward and forward to the concave hind edge of the spreading
arms of the orbital portion of the interorbital process of the parasphenoid, the lateral edges of the
membrane, postero-ventral to those arms, being attached, on either side, to the mesial edge of the
nearly vertical orbital portion of the corresponding proötic. Against that part of this membrane
that lies between the orbital portions of the proötics, or immediately postero-ventral to it, lies the
pituitary body, the entire opening closed by the membrane, or at least that part of it that lies between
the proöties, accordingly being the pituitary opening of the brain case. The whole opening may be
referred to as that opening.

The ventral one of the two usually confluent perforations of the interorbital wall of Dactylo-
pterus thus lies between a membrane that fills the pituitary opening of the brain case and a process
of the parasphenoid the dorsal end of which fulfils the function of a basisphenoid, if it be not in part
that bone. On the antero-dorsal portion of the osseous boundary of this ventral perforation of the
interorbital wall, and partly also on the ventral surface of the membrane that closes the pituitary
opening, a median vertical membrane has its attachment. Ventro-posteriorly this membrane becomes
less strong, and separates into two parts which spread to either side and are doubtless attached to
the parasphenoid, though this could not be satisfactorily determined in my material. The membrane
is thus a median vertical one which closes, more or less completely, the ventral perforation. On
the dorsal portion of this membrane, in 5 cm specimens, and directly opposite its fellow of the opposite

— 164 —

side, the rectus externus muscle has its origin. Ventro-anterior to the rectus externus, and also
wholly on the membrane, the rectus internus has its origin. The rectus inferior runs upward and
backward lateral to the rectus internus, and has its origin in’ part on the posterior portion of the
membrane that closes the optice fenestra and in part on the adjoining and bounding portions of the
interorbital process of the parasphenoid. The reetus superior runs downward posterior to the rectus
inferior, anterior to the reetus externus, and lateral to the rectus internus, and has its origin on the
dorsal surface of the parasphenoid. The pituitary vein forms a transverse commissure across the
dorsal surfaces on the recti interni, and, on either side, runs dorso-posteriorly to join the jugular
vein as that vein enters the trigemino-facialis chamber. The internal carotid artery traverses a
canal that lies wholly in the parasphenoid, traversing that bone from its ventral surface to issue
on the dorsal surface in the region of the ventral perforation of the interorbital wall. There it gives
off the orbito-nasal artery, and, joining its fellow of the opposite side, passes upward in the
middle line, between the recti interni and immediately anterior to the transverse commissure of
the pituitary veins, and, piereing the membranous floor of the cranial cavity, enters that cavity.
Immediately anterior to the communicating branch to the internal carotid, the afferent pseudobranchial
artery communicates with its fellow of the opposite side by a cross-commissural branch which
traverses the ventral perforation of the interorbital wall.

The ventral perforation of the interorbital wall of Daetylopterus, and some indeterminate
but adjoining portion of the hind end of the orbit, is thus a myodome strietly comparable to that
of the other fishes of the group, but it is so short, antero-posteriorly, that it appears transverse
instead of longitudinal in position. In Scorpaena the myodome extends almost to the hind end of
the basioceipital. In Peristedion it has been considerably shortened, and extends, as it does in Amia,
only to the hind edges of the proöties. In Dactylopterus, it has been still further shortened, and,
as a result of this shortening, some portion of the proötic bridge has been tilted upward so that it
lies in a nearly vertical transverse position and forms an apparent part of the hind wall of the orbit:
the myodome being, so to speak, squeezed or shoved out of the brain case into the hind end of
the orbit.

The PARASPHENOID is a broad flat bone the principal features of which have just above
been described in deseribing the orbit. It suturates anteriorly with the vomer and ectethmoids,
posteriorly with the basioceipital, and laterally, in its posterior portion, with the proöties. Dorsally
it is in sutural contact, by its interorbital process, with the alisphenoids. Its ascending process,
on either side, is a small pointed process which suturates with the ventral end of the sharp angle
that separates the lateral and orbital surfaces of the proötic. On the dorsal surface of the bone,
between these processes, there is a transverse ridge, already described, and posterior to this ridge
the dorsal surface of the bone is flat and smooth, without the median longitudinal ridge usually here
found on the bone. This seems to indicate, as will be more fully discussed below, that the transverse
ridge represents the longitudinal ridge usually found in other fishes, but here greatly shortened. The
ridge is tall and thin and inclines upward and backward, and on its posterior surface, in the median
line, there is a large pit-like depression. The internal carotid foramina perforate the bone, instead
of lyıng between it and the proötics.

The BASISPHENOID is either wanting or is indistinguishably fused with the interorbital
process of the parasphenoid.

— 165 —

The ALISPHENOID, as seen from the outside of the skull, is a sub-semicireular bone, the
curved edge directed ventrally and deeply notched to form the superior border of the optic fenestra.
Immediately anterior to this fenestra,'the ventral edge of the bone suturates with the dorsal edge
of the middle region of the interorbital process of the parasphenoid, while anterior to that region of
sutural contact it is in synchondrosis with the cartilage of the interorbital wall. Posterior to the
optie fenestra it suturates with the proötic, the hind corner of the bone being in synchondrosis with
a small interspace of cartilage that lies between it and the proötic and sphenotic. On the internal
surface of the bone there is, as in the other fishes of the group, a large brace-like process which
separates the mid-brain and fore-brain recesses of the cranial cavity. The dorsal edge of this process
is greatly expanded, as is also the dorsal edge of the bone itself, the large flat surface thus formed
giving support mainly to the frontal; but the hind corner of the brace-like process extends backward
beneath the anterior edge of the supraoceipital and so gives support to that bone also.

The alisphenoid is perforated, in the adult, immediately posterior to the optic fenestra, by
a small foramen which doubtless transmits the nervus trochlearis; that nerve traversing the optie
fenestra, close against the alisphenoid, in 5 cm specimens. Near its dorsal edge the bone is traversed
by a small canal which transmits a branch of the orbito-nasal vein, accompanied by a general
cutaneous branch from the r. oticus trigemini. The bone is not traversed, as it is in the other fishes,
by the lateralis branch that innervates the terminal organ of the supraorbital canal, that branch
passing upward external to the alisphenoid and then perforating the frontal.

The SPHENOTIC isa small and irregular bone and is, in all my specimens, inseparably ankylosed
with the postfrontal, which latter bone lies upon and occupies about one half of the dorsal surface
of the sphenotic. The remainder of the dorsal surface of the sphenotie gives support mainly to the
pterotic, a small corner only of the bone supporting the hind edge of the frontal. In the fusion of
the sphenotic with the postirontal, Dactylopterus resembles Polypterus, which latter fish is the
only other one in which, as I have stated in a recent work (’04, p. 56), I know this fusion to be of
reoular occurrence. Ridewood, since the publication of that work, has said (’04a, p. 56) that the
fusion of these two bones is also of almost constant oceurrence in Amia, their separation in that fish,
being an „occasional feature only‘“. While this may be true of aleoholie or otherwise preserved speci-
mens, it certainly is not of fresh material.

The sphenotic is in sutural contact with the proötie and pterotie but not with the alısphenoid,
being separated from the latter bone by a small interspace of cartilage. On the lateral edge of the
bone there is a stout process which gives articulation to one of four articular processes on the dorsal
end of the hyomandibular, the particular process here concerned apparently being the regular anterior
articular head of the hyomandibular, as will be later explained. Immediately dorsal to this artieulating
process there is, on the same edge of the sphenotic, a sharp process which gives support, on its lateral
surface, to the small postorbital bone; probably also giving insertion to a part of the levator arcus
palatini muscle, though this was not investigated.

Between the sphenotic and pterotic there is a large and deep dilatator fossa, roofed by the
pterotic and sphenotic, the postfrontal apparently not coming into roofing relations with it. The
anterior wall of the fossa is perforated by a large foramen which transmits the ramus oticus.

The PROÖTIC is a large bone with orbital and lateral portions, these two portions being
separated from each other by a tall and ridge-like edge which, because of the flattened condition

— 166 —

of the head, lies in a nearly horizontal position directed postero-laterally and but slightly upward.
This ridge-like postorbital edge is perforated by a large opening which represents the trigemino-
facialis chamber, and from this chamber five foramina lead into the cranial cavity. One of these
foramina transmits the truncus ciliaris profundi accompanied by the encephalic branch of the jugular
vein; a second one transmits the ramus ophthalmicus lateralis; a third the truncus trigeminus and
related lateralis nerves, and a fourth the truncus facialis. The fifth foramen certainly transmits
the nervus abducens, and probably that nerve alone, the palatinus facialis doubtless traversing the
facialis foramen, but these nerves were not traced in the adult. In 5 cm specimens, they both traverse
the ventral portion of the facialis foramen, enter the trigemino-facialis chamber, and traversing
that chamber, issue through its trigeminus opening. The chamber is also traversed, as usual, by
the jugular vein and the truncus sympatheticus.

Dorsal to the trigemino-facialis chamber, the tall postorbital edge of the proötic expands
abruptly and bears, on this expanded portion, an elongated and curved artieular surface the axis
of which is direeted dorso-posteriorly while the surface itself is directed laterally. This surface gives
sliding artieulation to a curved surface on the anterior one of the four artieular heads of the hyoman-
dibular. Slightly dorsal (here lateral) to this articular surface the bone is connected by synchondrosis
with the sphenotic.

The orbital portion of the proötie is large, is transverse and nearly vertical in position, inclining
upward and slightly forward, and arises from the internal surface of the lateral portion of the bone
sliehtly posterior to its anterior edge. Near its dorsal edge it. is perforated by the oculomotorius
foramen. Its mesial edge does not reach the middle line, a small ventral portion of the edge suturating
with the transverse ridge on the dorsal surface of the parasphenoid, while the dorsal portion of the
edge is free and forms part of the boundary of the pituitary opening. The lateral portion of the bone
has its ventro-mesial edge bevelled on its outer surface, and there suturates with the lateral edge
of the parasphenoid. Internal to this line of sutural contact, and posterior to the orbital portion of
the bone, the edge of the proötie is slightly grooved and this groove lodges the lateral edge of a broad
band of cartilage which extends across the middle line to the corresponding edge of the proötie of the
opposite side. The hind edge of the band is lodged in a groove on the anterior edge of the basioceipital,
its anterior edge reaching to the posterior surface of the transverse ridge on the dorsal surface of the
parasphenoid. This anterior edge of the cartilage seems not to be a free edge, but to rather abruptly
but insensibly pass into a delicate membrane which is connected, anteriorly, with the stouter mem-
brane that fills the pituitary opening of the brain case. Two suppositions are accordingly possible
to explain the conditions here; either the postpituitary portion of the proötic bridge has been depressed
and appressed upon the underlying ventral flanges of the proötics, as assumed by Gill (’91a, p. 379)
in his descriptions of Hemitripterus, or the entire proötie bridge has been shortened and shoved
forward nearly to the anterior edges of the ventral flanges of the proötics and there tilted upward
to form, on either side, the orbital portion of the corresponding bone. The conditions found in
Blennius, to be later described, indicate that the first of these two assumptions is probably the proper
one, but they also indicate that the process has not been simply one of depression and appression
of the proötic bridge, but also one of reduction of the ventral flanges of the proötics. These ventral
flanges have, apparently, been so greatly reduced that they are practically suppressed, and the
primary floor of the eranial cavity is here formed by the proötic bridge alone, that bridge Iying
directly upon the parasphenoid. The hypöphysial fenestra is then represented, in its posterior

oT

portion in that long and wide space that lies between those surfaces of the proöties of either side
that suturate with the lateral edges of the parasphenoid, while in its anterior portion it is
represented in the space that lies between and anterior to the orbital portions of the proöties,
this space opening onto the floor of the myodome and being filled by the transverse ridge on the
dorsal surface of the parasphenoid. This latter ridge on the parasphenoid is accordingly the greatly
shortened and widened homologue of the longitudinal ridge on the bone in the other fishes of the
group. A result of this arrangement is that the pituitary opening of the brain case is partly filled,
toward the orbit, by the transverse ridge on the parasphenoid, and that the hind end of the pituitary
opening is confluent with the hypophysial fenestra at the hind end of that portion of the fenestra
that opens onto the floor of the myodome.

The lateral surface of the proötic has dorsal and ventral regions separated by a pronounced
but rounded angle which starts from the dorsal edge of the trigemino-facialis chamber and runs
postero-mesially to the hind edge of the bone. The dorsal portion of the surface forms the anterior
portion of a large subtemporal fossa, described below. On the internal surface of the bone, and
parallel with this dorsal portion of its lateral surface, there is a tall flange of bone which projects
{rom below upward and forms the anterior wall of the labyrinth recess. The dorsal edge of this flange
is partly capped with cartilage and there gives support to the hind edge of the frontal and to the
parietal, the hind edge of the flange projecting postero-mesially beneath the supraoceipital and there
being continuous with a slight ridge on the internal surface of that bone. The deep tall space between
the flange and the lateral wall of the bone is continued dorso-antero-laterally by a slight recess on the
internal surface of the sphenotic, and the large recess thus formed between the two bones lodges
not only the anterior semicireular canal and the anterior portion of the utriculus, but probably also
the anterior end of the sacculus, for there is no differentiated saceular groove. The recess must
also lodge an anterior portion of the external semicireular canal, for that canal leaves the recess
near its dorso-antero-lateral corner to enter it own special canal in the pterotic. The exact relations
could not be determined because of the want of sufficient material.

Anteriorly the proötie is bounded by, and is partly in synchondrosis and partly in sutural
connection with the alisphenoid. Dorsally and posteriorly it is in similar relations with the sphenotie,
pterotic, basioccipital and exoccipital. Ventrally it is overlapped externally by and is suturally
connected with the parasphenoid.

The PTEROTIC has, more than in the other fishes of the group, the appearance of being
formed of two separate and independent components secondarily fused with each other, for, although
the two components have the same length, they are not exactly superimposed; the dermal component
projecting forward beyond the primary component, and this latter component projecting posteriorly
beyond the dermal one. This projeceting portion of the primary component supports the anterior
edge of the suprascapular.

The dermal component of the bone is bounded, as usual, by the frontal, postirontal, parietal,
lateral extrascapular (rocher) and suprascapular, and the lateral half of this part of the bone is bent
abruptly downward, as are also corresponding portions of the postfrontal and suprascapular, a rounded
longitudinal angle thus being formed, which extends across the three bones and terminates, at teh
hind end of the suprascapular, in a strong spine. This component of the pterotie is thus an angular
bone placed longitudinally along the lateral edge of the dorsal surface of the skull. It is traversed
by the main infraorbital latero-sensory canal and lodges three sense organs of that line, two innervated

— 16852, —

by the oticus lateralis and one by the supratemporalis lateralis vagi. Near the middle of the bone,
between the organs innervated by the oticus and supratemporalis lateralis vagi, the main infraorbital
canal anastomoses with the dorsal end of the preopercular canal.

The primary component of the pterotic has a thickened anterior portion but is elsewhere
a thin plate of bone which lines the ventral surface of the angular dermal component of the bone.
It is traversed by the external semicircular canal, but otherwise has no bounding relations to the
cranial cavity. This is due to the presence of a large and deep depression on the lateral surface of
the brain case, this depression pinching the skull, so to speak, to such an extent that the primary
component of the pterotie has been pressed upward against the under surface of its dermal component,
has ceased to form part of the apparent lateral surface of the brain case, and simply lines the ventral
and ventro-mesial surfaces of the overhanging roof of the depression. This depression includes both
the proötie and subtemporal fossae of Scorpaena, and it has, in addition, a large posterior extension
which lies posterior to the arch of the external semicircular canal and is not found in Scorpaena. The
entire depression may, however, be called the subtemporal fossa, the fossae of opposite sides giving
to the brain case, in ventral views, an hour-glass-shaped appearance. The adductores hyomandi-
bularis and opereuli have their origins in the fossa, arising mainly on a band of cartilage that separates
the pterotic from the exoccipital. The levators of the first four branchial arches have their origins
in the anterior portion of the fossa, anterior to the adductor hyomandibularis, while the fifth levator
muscle has its origin ventro-mesial to the adductor operculi, between that muscle and the foramına
for the vagus and glossopharyngeus. This fifth levator perforates, to reach its surface of origin,
a mass of tissue that looks like degenerate glandular tissue and that must be the homologue of what
I considered as the thymus in Amia (°97, p. 643). Whatever it may be, this tissue fills the entire fossa
ventro-mesial and posterior to the adduetores hyomandibularis and opereuli, and the fossa would
seem to be developed in some relation to it rather than as any consequence of the origins of the several
muscles here.

On the anterior edge of the thickened anterior portion of the primary component of the pterotie
there are two fossae, the larger, mesial one Iying on the internal surface of the bone while the smaller,
lateral one lies on its external surface. The mesial fossa lodges the anterior portion of the external
semieircular canal, and is in communication with the dorso-antero-lateral end of the tall recess already
described on the internal surface of the proötic and sphenotic; the posterior portion of the semieircular
canal traversing the thin posterior portion of the auto-pterotic, and forming a prominent ridge on
its external surface. The lateral one of the two fossae forms the posterior half of the dilatator fossa,
the anterior half of that fossa lying in the sphenotic. Immediately posterior to the dilatator Tossa,
and so placed that it seems to form part of themouth of that fossa, there is, on the external surface of the
auto-pterotic, a large round articular fossa which gives articulation to the regular posterior artieular
head of the hyoniandibular. The hind edge of this articular fossa is thickened and grooved to form
an elongated, transversely placed and slishtly convex articular surface, which gives a sliding artieu-
lation to the posterior one of the four articular heads of the hyomandibular. Immediately dorso-
lateral to this articular surface is the perforation by which the preopercular latero-sensory canal
joins the main infraorbital canal.

The auto-pterotic is bounded anteriorly by the sphenotic and proötic, and also by a small
interspace of cartilage between the adjoining edges of those two bones. It is separated from the
exoceipital by a band of cartilage, and beneath (dorsal to) this band it is in contact with the lateral

— 169 —

edge of the epiotic. The hind end of the bone gives support, as already stated, to the anterior end
of the suprascapular.

The pterotic of Dactylopterus thus has no exposed surface corresponding to the one that
forms part of the lateral bounding wall of the temporal fossa in the other fishes of the group. That
portion of the temporal fossa that is usually bounded by this bone is thus either wholly absent in
Dactylopterus, or it has been reduced, by the compressive action that has given rise to the subtemporal
fossa, to a narrow space that lies between the pterotic-exoceipital band of cartilage, just above referred
to, and the overlying dermal bones on the dorsal surface of the skull. The band of cartilage is evidently
the homologue of the cartilage that forms the bottom of the temporal fossa in the other fishes, and
as this cartilage is certainly not in synchondrosis with the overlying dermal bones, a thin space must
exist between them, in the place where the temporal fossa is usually found. A further possibility
regarding a portion of the fossa will be referred to when describing the suprascapular.

The BASIOCCIPITAL is broad and thin, is slightly convex on its internal and slightly concave
on its external surface, and the median longitudinal line on its ventral surface presents a slight
reöntrant angle. On the hind end of the bone there is a deep median pit which extends forward to
the line of the reöntrant angle and represents the vertebral depression on the hind end of the bone.
Lateral to this pit, the wide flange-like portions of the bone give support, on their dorsal surfaces,
to the ventral edges of the exoceipitals. Anteriorly the bone suturates with the proöties and para-
sphenoid. A very slisht depression on either side of the internal surface of the bone forms the hind
end of the saccular groove. Between these two depressions there is, in the anterior portion of the
bone, a slight median depression, the significance of which could not be determined in my limited
material. The anterior edge of the bone is grooved, and encloses the hind end of the thin median
sheet of cartilage that connects the ventral edges of the proöties of opposite sides. The median
portion of the hind edge of the dorsal surface of the bone forms the ventral boundary of the foramen
magnum.

The EXOCCIPITAL has a concave lateral and a strongly reöntrant posterior surface. The
latter surface has the two usual portions, one of which forms part of the hind wall of the cranial
cavity while the other arches over the medulla, the two portions appearing, in the disartieulated bone
as a stout, tall, V-shaped ridge arising from the dorso-mesial surface of a sub-oval bone. That part
of the posterior portion of the bone that arches over the medulla has a thick dorso-mesial edge, which
suturates in part with its fellow of the opposite side but mainly with the ventral edge of the spina
oceipitalis. The dorsal edge of that part of the bone that forms part of the hind wall of the cranial
cavity suturates with the ventral edge of a strong ridge on the ventral surface of the epiotie, this
ridge forming the posterior surface of the latter bone. Slightly antero-lateral to this ridge on the
epiotic, a relatively large V-shaped portion of the ventral surface of that bone is in sutura] contact
with a corresponding surface on the dorso-mesial surface of the lateral plate of the exoceipital; this
latter surface of contact extending downward from the dorsal edge of the exoceipital nearly to the
central point of the bone. Between the portions of these two bones that have these two sutural
connections — the lateral and posterior plates of the exoccipital, below, and the epiotie above —
there is a tall and narrow space which must lodge the posterior portion of the external semieircular
canal, the larger portion of the posterior canal, and possibly also the hind end of the utrieulus; but
want of material prevented my determining the exact relations. A broad, low and rounded ridge

Zoologiea. Helft 57. ‚ pp)

— 10 —

on the outer surface of the exoceipital marks the position of the dorso-lateral portion of this labyrinth
space, and forms a continuation of the ridge on the pterotie that marks the course of the external
semicireular canal in that bone.

The dorsal edge of the exoceipital reaches the ventral surface of the overhanging roof of the
skull and is there separated by a relatively wide band of cartilage from the ventral edge of the
pterotic, that edge of the latter bone here being presented mesially. This band of cartilage forms a
nearly longitudinal line along the bottom (roof) of the subtemporal fossa, and lies against the ventral
surfaces of the parietal and lateral extrascapular.

On the hind edge of the lateral plate of the exocecipital there are two flat stout processes sepa-
rated by a deep and rounded incisure. The dorso-lateral process suturates with the pedicle of the
suprascapular, the ventro-mesial one suturating with, instead of articulating with, a process on the
anterior edge of the first vertebra. Antero-internal to the incisure between the bases of the two
processes, a canal traverses the medullary plate of the bone, transmitting the oceipital nerve or nerves.
Ventrally the exoceipital suturates with the basioccipital, in the manner already explained. On
the lateral surface of the bone there is a small foramen which doubtless transmits the nervus
glossopharyngeus, and posterior to that foramen there is a large pit, in the bottom of which there
are two to four foramina which open into the cranial cavity and doubtless transmit the nervus
vagus alone; the actual relations of these nerves to the bone not being determined for the reasons
alrcady given.

The EPIOTIC is a small bone that seems at first sight to bear no resemblance whatever to
the pyramidal bone of the other fishes of the group. The dorsal surface of the bone is flat and sub-oval
in shape, and on the ventral surface of this thin dorsal plate there are two relatively tall and thin
flanges. One of these flanges is straight and extends from about the middle of the mesial edge of
bone, postero-laterally to its lateral edge, the ventral edge of the flange suturating with the posterior
plate of the exoccipital. The postero-mesial surface of this flange is exposed externally, and forms
a surface strietly comparable to the postero-mesial surface of the bone in the other fishes of the group.
The second flange lies anterior to the first one and is strongly curved, the hollow of the curve direeted
forward and both ends of the flange reaching the antero-lateral edge of the bone and there vanishing.
The space enclosed within the curve of this flange is roughened and suturates with the dorso-mesial
surface of the lateral plate of the exoceipital, as already stated. This roughened surface of the
epiotie thus corresponds to the ventral edge of that surface of the bone in the other fishes that forms
part of the mesial wall of the temporal groove. The temporal-groove surface of the bone of Dactylo-
pterus is accordingly wholly wanting, or at most is only represented in a part of the thin lateral edge
of the bone, this edge being covered laterally and ventrally by the band of cartilage already described
between the pterotic and exoccipital.

Between the two flanges on the ventral surface of the epiotie there is a space which forms
the dorsal portion of that part of the labyrinth recess which, as just above explained, must lodge
the posterior semicircular canal and the posterior portion of the external canal. The dorso-postero-
lateral portion of this labyrinth space is bounded externally here ventrally by the band of cartilage
between the pterotic and exoceipital; temıporal and posterior surfaces of the epiotie not here uniting
to form an angle which encloses the summit of the posterior canal, as in the other fishes. The large
flat dorsal surface of the epiotic gives support to adjoining portions of the parietal, lateral extra-
scapular and mesial extrascapular, and its mesial edge is in sutural contact with the lateral edge

— al —

of the supraoccipital. The thin plate that forms this part of the bone projects posteriorly beyond
the flange that forms the posterior surface of the bone, the two plates forming part of theroof and
part of the bottom (antero-lateral corner) of a large fossa on the posterior surface of the skull. The
postero-lateral end of the flange that forms the posterior surface of the bone, and adjoining portions
of the lateral edge of the bone, suturate respectively with the pedicle and body of the suprascapular.

The SUPRAOCCIPITAL, the interparietal of Cuvier and Valenciennes’ descriptions, has
the usual dorsal and ventral limbs, and a large spina occipitalis. The dorsal limb of the bone, with
the exception of two small lateral processes on either side, comes everywhere to the outer level of
the dorsal surface of the skull, and has surface markings exactly similar to those on the adjoining
dermal bones; and this apparently dermal portion of this limb of the bone extends posteriorly
sliehtly beyond the line of origin of the ventral limb, onto the dorsal surface of a dorsal plate-like
portion of the spina oceipitalis. This limb of the bone suturates anteriorly with the frontals, laterally
with the parietals, and posteriorly with the mesial extrascapulars; its anterior edge resting, on
either side, upon the hind end of the expanded dorsal surface of the brace-like ridge on the internal
surface of the alisphenoid. On the ventral surface of the dorsal limb, beginning immediately anterior
to the line of origin of the ventral limb, there is, on either side, a small ridge which, extending antero-
laterally is continuous with that tall ridge on the internal surface of the proötie that forms the anterior
wall of the labyrinth recess. The antero-lateral end of this ridge on the supraoceipital forms one of
the two lateral processes on either side of the dorsal limb of the bone, the other process Iyıng
immediately posterior and parallel to it, giving support on its dorsal surface to the parietal, and being
in synchondrosis, by its postero-lateral edge, with the antero-mesial edge of the epiotie.

The ventral limb of the supraoceipital is irregular, as shown in the figures, and has on either
side a strongly concave dorsal and convex ventral surface. Along the median line of the limb a thin
median vertical plate of bone arises supported on either side by a similar but slightly inclined plate,
these three plates forming the vertical portion of the spina oceipitalis. This vertical portion of the
spina supports, on its dorsal edge, a flat broad thin plate which forms a direct posterior extension
of the dorsal limb of the bone, and gives support, on either side of its dorsal surface, to the corres-
ponding mesial extrascapular. The lateral edge of the anterior end of this flat portion of the spina,
on either side, rests upon and is coalesced with the dorsal edge of the lateral portion of the ventral
limb of the bone, a deep pocket thus being formed on either side of the posterior surface of the bone,
this pocket forming the dorso-mesial corner of a large fossa on either side of the hind end of the skull.
The posterior half of the ventral surface of the ventral limb of the bone rests, on either side, on the
dorsal edge of the medullary plate of the corresponding exoceipital, either suturating or being in
synchondrosis with that bone. Lateral to the exoceipital, the ventral limb of the supraoccipital
is in similar contact with the mesial edge of the epiotic.

There is no separate OPISTHOTIC bone, nor is there any indication of the fusion of this bone

with any of the other bones.

The primary bones, and their relations to the dorsal surface of the primary skull, now having
been described, the dermal bones that overlie them and form the casque-like dorsal surface of the
skull can be described.

The two NASALS have fused in the median line to form a single median bone, and have
already been described.

ee

The FRONTAL is an eight-sided bone, each side being straight or slightly concave. One
of these sides forms the middle portion of the dorsal margin of the orbit, another suturates with the
frontal of the opposite side, the others suturating with the ectethmoid, nasal, supraoeccipital, parietal,
pterotic and postfrontal. The bone has no ventral flange. It rests upon the expanded dorsal edges
of the body and brace-like internal process of the alisphenoid, on a small portion of the sphenotiec,
and on a small projecting shelf from the deeper layers of the anterior edge of the supraoceipital. It
is traversed by the supraorbital latero-sensory canal and lodges five organs of the line, as will be
later fully described.

The POSTFRONTAL is a small dermal bone that lies upon and is inseparably fused, in all
of my adult specimens, with a lateral portion of the dorsal surface of the sphenotie. It suturates
with the frontal and dermo-pterotic, and is traversed by the main infraorbital latero-sensory canal,
lodging one organ of that canal, innervated by the oticus lateralıs.

The PARIETAL is a sub-oval bone, bounded anteriorly by the frontal, laterally by the
pterotie, posteriorly by the lateral and mesial extrascapulars, and mesially by the supraoceipital.
It rests upon the dorsal surface of the epiotie, upon the dorsal edges of those flanges of the proötic
and supraoceipital that form the antero-mesial wall of the labyrinth recess, and also upon a small
shelf projecting mesially from what are apparently the deeper layers of the dermal portion of the
pterotic.

The LATERAL EXTRASCAPULAR is a small oval bone traversed by the lateral portion of
the supratemporal commissure of the latero-sensory canals, and lodging one organ of that canal.
It is not traversed by the main infraorbital canal, but a groove on its lateral edge lodges a short
section of that canal, apparently without related organ, as will be further explained when describing
the canals. It is bounded antero-mesially by the parietal, antero-laterally by the pterotie, postero-
laterally by the suprascapular, and postero-mesially by the mesial extrascapular. It has no bounding
relations either to the subtemporal fossa or to the large fossa on the posterior surface of the skull,
its ventral surface being entirely covered by the epiotic, pterotic and suprascapular, on which bones
it rests.

The MESIAL EXTRASTAPULAR is a large subrectangular bone with straight and nearly
parallel lateral and mesial edges. It is traversed by the mesial section of the supratemporal com-
missure and lodges one organ of that commissure. It suturates, in the middle line, with its fellow
of the opposite side. Anteriorly, it is bounded by the supraoceipital and parietal, and laterally by
the lateral extrascapular and suprascapular. Its mesial third, approximately, lies upon the broad
flat dorsal surface of the spina oceipitalis, its lateral third resting upon a shelf-like portion of the
mesial edge of the suprascapular. Between those two bones it forms part of the roof of the large
fossa on the corresponding side of the posterior surface of the skull.

The SUPRASCAPULAR is a large bone with a prolonged and pointed hind end. It is bounded
anteriorly by the pterotic, antero-mesially by the lateral extrascapular, and mesially, along the
anterior half only of its length, by the mesial extrascapular. The lateral half of the bone is bent
downward at an angle to the mesial portion, as already stated, and along this angle there is a stout
ridge which begins at the anterior quarter of the bone and extends backward to its pointed hind end.
The bone is traversed by the main infraorbital latero-sensory canal and lodges one organ of that line,
innervated by a branch of the supratemporalis lateralis vagi. This organ, in 5 em speeimens, is much

— 173 —

larger than the other organs of the line, and may perhaps represent the two organs usually found
one in this bone and the other in the supraclavicular in the other fishes of the group.

On the ventral surface of the bone there is a stout V-shaped flange, projeeting ventro-antero-
mesially. The line of origin of the anterior limb of the V begins at the rounded antero-mesial corner
of the bone, and from there runs postero-laterally until it reaches the angle between the mesial and
lateral portions of the bone. There it turns postero-mesially, nearly at a right angle, and so continues
until it reaches the mesial edge of the bone at about its middle point. From this right-angled line
of origin, the V-shaped flange projects ventro-antero-mesially, its two limbs and the overlying
body of the bone enclosing a sub-pyramidal space which forms the lateral, recess-like corner of the
large fossa on the hind end of the corresponding half of the skull. The angle of the V-shaped flange
is thickened, and its ventral end suturates with the exoccipital, the dorsal portion of the mesial edge
of the anterior limb of the flange suturating with the postero-lateral end of that flange on the internal
surface of the epiotic that represents the posterior surface of that bone. At the dorso-mesial corner
of the anterior surface of the anterior limb of the flange on the suprascapular, there is a small recess
which lodges but is not in synchondrosis with the hind end of the band of cartilage that lies between
the pterotic and exoceipital. The mesial edge of the suprascapular here closely approaches the lateral
edge of the dorsal plate of the epiotie, but apparently does not touch that bone. The V-shaped flange
of the suprascapular must accordingly certainly contain the opisthotie process of the bone, and it
probably represents both that process and the epiotic process, joined by a web of bone which entirely
closes the space usually occupied by the posterior opening of the temporal fossa. However this may
be, a posterior opening of a temporal fossa is wholly wanting in this fish, and if any portion of the
fossa exists it must open on the lateral surface of the skull and hence be represented in the posterior
portion of the large subtemporal fossa. In certain specimens of Cottus octodecimospinosus, I have
already shown that the posterior opening of the temporal fossa may be entirely closed by the invading
growth of its bounding bones, the fossa then opening wholly on the lateral surface of the skull. In
such a fish, if the subtemporal fossa were to be greatly deepened, as it is in Dactylopterus, it would
inevitably absorb and incorporate in itself a posterior portion of the adjoining termporal fossa. But
in that case the epiotic should form part of the bounding wall of the fossa, and I can not find that
it does so in Dactylopterus; the epiotic here apparent)y being everywhere covered by the hind end
of the pterotie-exoccipital band of cartilage which lies in the bottom (roof) of the fossa. The lateral
edge of the epiotic, immediately anterior to the pedicle of the suprascapular, comes close to the
lateral edge of the pterotic-exoceipital cartilage and may there perhaps be exposed, thus forming
part of the bounding wall of the subtemporal fossa. Furthermore, the subtemporal fossa, as defined
by Sagemehl, is said to be an excavation of the cranial wall within the arch of the external semi-
eircular canal, but, in Dactylopterus, the fossa has a large portion which lies posterior to that canal.
This posterior extension may therefore represent the posterior portion of the temporal fossa of the
fish, here incorporated in the subtemporal fossa by the unusual development of the latter.

On the ventral surface of the suprascapular, close against or even cutting into the lateral edge
of the base of the posterior limb of the V-shaped pedicle, there is a deep circular pit, so deep that it
shows, on the dorsal surface of the prepared skull, as a eireular translucent spot in the bone. This
pit gives origin to strong fibrous tissues which have their insertion on the dorsal end of the clavicle,
that end of the clavicle not apparently entering the pit, in prepared specimens, but the pit being
quite certainly developed in articular relation to it. At the anterior margin of the pit there is a slight

— 174 —

depression which gives articulation to the dorsal end of a long, slender, gutter-shaped and tapering
bone, which is applied to the antero-lateral surface of the dorsal end of the clavicle and is certainly
the SUPRACLAVICULAR. This bone is not traversed by the main infraorbital canal, and its
latero-sensory component must be represented either in a part of the unusually large suprascapular
or in a small bone that lies along the postero-lateral edge of the suprascapular and is traversed by
the main infraorbital canal after it leaves that bone.

On either side of the hind end of the skull there is a large and deep fossa, already several
times referred to. This fossa oceupies the entire posterior surface of either side of the skull, and has
deep dorso-mesial and dorso-lateral corners. or recesses, and a shallow ventral one. It is bounded
by the mesial extrascapular, suprascapular, supraoceipital, epiotic and exoceipital, and there is nothing
comparable to it in any of the other fishes of the group. Want of material prevented a proper
investigation of it, but it is largely, if not entirely filled by an anterior prolongation of the swim-
bladder: the dorsal wall of this portion of the bladder lying close against the ventral surface of the
dermal bones that form the roof of the fossa, and the lateral surface of the bladder having closely
applied to it a band-like anterior prolongation of the trunk muscles.

2. INFRAORBITAL CHAIN OF BONES.

The infraorbital chain consists of four bones, all of which are traversed by the main infra-
orbital canal. In addition to these four bones, there is a small bone, the pontinal of Gill, which extends
from the hind edge of the second bone of the series into a reöntrant angle on the anterior edge of the
preopercular.

The first infraorbital bone, or lachrymal, has a thickened anterior end which curves mesially,
and almost meets, in the middle line, its fellow of the opposite side. The dorsal edge of this part of
the bone is slightly grooved and articulates moveably with the antero-ventral edge of the nasal, the
dorsal edge of the lachrymal lying upon and being strongly but somewhat loosely bound to the outer
surface of the lachrymo-palatine process of the nasal. Internal to the hind end of this grooved
portion of the lachrymal, there is, on the internal surface of the bone, a short transverse ridge with
a convex outer edge, and slightly posterior to this ridge there is a second but shorter ridge; these
two ridges and the groove between them having a sliding articulation with the palatine on the dorso-
lateral surface of its maxillary process, as will be later explained. Slightly ventro-posterior to these
two articular ridges, a strong brace-like process arises from the internal surface of the lachrymal,
projeeting dorso-postero-mesially. The dorsal end of this process is large, lies in the level of the
dorsal edge of the bone, and has on its dorsal surface a large oval facet which articulates with the
lachrymal articular eminence of the ectethmoid. The hind edge of the articular facet suturates with
the anterior edge of the orbital shelf of the second infraorbital bone, the hind edge of the lachrymal
itself suturating with the second and third infraorbital bones; the second infraorbital Iying ventral
to the third one and having no bounding relations to the orbit. The bone is traversed by the main
infraorbital latero-sensory canal and lodges three sense organs of that line.

The second infraorbital bone is an elongated one, bounded anteriorly by the first and dorsally
by the third bone of the series. The main infraorbital canal enters it at its anterior edge, runs hori-
zontally backward in it and then turns upward and forward at an acute angle, to leave the bone on
its dorsal margin and enter the third bone of the series; this section of canal lodging two sense

I

organs. The ventro-posterior corner of the bone is prolonged into a short process which has articular
surfaces for artieulation with the pontinal.

The pontinal is a small and somewhat elongated bone, which extends from the second infra-
orbital into a reöntrant angle on the anterior edge of the preopercular, articulating with and being
firmly bound to each of these two bones. It does not lodge any part of the latero-sensory canal,
and is accordingly either an independent dermal ossicle or a detached portion of the second infra-
orbital bone.

The third infraorbital bone bears, along the internal surface of its orbital margin, a large thin
projecting plate of bone which forms about one half of the floor and a corresponding part of the posterior
wall of the orbit. The central portion of this orbital shelf is supported by a bracing web of bone
which arises from the internal surface of this bone and is continued beyond it onto the internal surface
of the second infraorbital bone, near its hind edge. From the internal surfaces of the adjoining edges
of these two infraorbital bones, immediately anterior to the bracing web, a strong ligament arises,
and running forward has its insertion on the ventral surface of the dorsal limb of the dentary. The
anterior end of the orbital shelf projects forward beyond the anterior edge of the body of the bone,
along the inner surface of the first infraorbital, and comes into sutural contact with, and is firmly
bound to, the hind edge of the dorsal end of the brace-like articular process of the latter bone. The
bone is traversed by the main infraorbital latero-sensory canal and lodges three organs of the line.

The fourth infraorbital is a small bone, postorbital in position, that is in contact ventrally
with the third infraorbital and dorsally with the postfrontal. It transmits the latero-sensory canal
from the former to the latter bone, lodging one organ of the line.

The first and third infraorbital bones are the preorbital and fourth suborPital, respectively,
of Gill’s descriptions; and these two bones and the second infraorbital, together, form the first sub-
orbital of Cuvier and Valenciennes’ descriptions. The second suborbital of Cuvier and Valenciennes
is the third suborbital, or pontinal of Gill’s desceriptions, but this bone, not being traversed by the
infraorbital canal, would seem not to properly be an independent element of the infraorbital series.

3. SUSPENSORIAL APPARATUS AND MANDIBLE.

The bones that form the hyomandibulo-palato-quadrate apparatus are firmly united to form
two pieces with a flexible joint between them. The posterior and much larger piece is formed by
the preopercular, hyomandibular, symplectic, quadrate and metapterygoid; and the anterior piece
by the palatine, the ectopterygoid and the entopterygoid. The flexible joint between the two pieces
is nearly transverse to the axis of the body of the fish, and permits that extensive lateral motion
of the hind end of the apparatus that easily places the large preopereular spine at an angle of more
than 45° to the axis of the body.

The PREOPERCULAR has a horizontal liimb, which terminates in the long and well known
spine, and a vertical limb which extends antero-dorsally at an angle of about 75° to the horizontal
limb. In the angle between the two limbs there is an articular facet, and immediately dorsal to this
facet an articular eminence, both of which give articulation to corresponding surfaces on the hind
end of the pontinal. The angle between the two limbs is spanned by a large web of bone which
arises from the deeper layers of the preopercular; and, external to this web, on either limb of the
bone, between the web and the outer surface of the thick, related limb, there is a large V-shaped

— 0 —

groove. The bone is traversed its full length by the preopercular latero-sensory canal, and lodges
SIXx sensory organs.

The HYOMANDIBULAR is an irregular bone, roughly triangular in general outline, one of
the angles of the triangle being direeted dorsally and bearing the articular heads of the bone. Not
far from the anterior edge of the triangle, and parallel with it, there is a slightly thickened portion,
which represents the shank of the bone. The hind edge of the triangle is slightly convex, and bears
on its external surface a tall ridge which projects laterally and slightly anteriorly. The posterior
surface of this ridge is applied against, and firmly bound to the antero-mesially presented anterior
surface of the dorsal limb of the preopereular, the dorsal end of the latter bone reaching to the lower
edge of the opercular process of the hyomandibular. This tall ridge along the hind edge of the hyo-
mandibular of Dactylopterus thus corresponds to the ridge that extends longitudinally along the
external surface of the shank of the bone in the other fishes of the group; but here, in Dactylopterus,
although the ridge begins on the external surface of the dorsal end of the slightly indicated shank,
it extends postero-ventrally at an angle to the shank, and leaves, between itself and the shank, a
wide intervening space which is spanned by a thin web of bone. The dorsal end of the ridge is
thickened to form a large articular head, which artieulates with the facet on the antero-lateral corner
of the squamosal, and is accordingly the regular posterior articular head of the bone. Postero-mesial
to this articular head there is a stout and bluntly pointed process, directed antero-dorsally in the line
of the ridge on the external surface of the bone. The postero-lateral surface of this process is slightly
concave, is grooved from its top to its base, and has a sliding articulation with the articular surface on
the thickened posterior edge of the articular facet on the squamosal. From the anterior surface of the
base of this articular process a strong process is directed antero-ventro-mesially. It expands at its
distal end, and has a curved articular edge which is presented mesially and has a sliding articulation
with the articular surface on the postorbital edge of the proötic immediately dorsal to the trigemino-
facialis chamber. Fused with the lateral edge of the base of this process of the hyomandibular, there
is a small process which arises from the anterior surface of the ridge on the external surface of the
bone, immediately ventral to the regular posterior articular head. This small process is direeted
anteriorly and has on its dorsal surface a slightly concave articular surface which artieulates with the
articular eminence on the sphenotic. This small process accordingly represents the regular anterior
articular head of the bone. Each of the two regular articular heads of the hyomandibular of Dactylo-
pterus thus has a related, accessory articular head which has a sliding articulation with the eranium,
this arrangement giving great solidity to the joint.

On the hind edge of the bone there is a short opercular process.

On the internal surface of the bone, immediately ventral to the bases of the two accessory
articular processes, there is a slight transverse ridge of bone, and on the dorsal surface of this ridge
is the internal opening of the facialis canal. This canal traverses the hyomandibular and opens on
its external surface immediately posterior to the slightly thickened portion that represents the shank
ofthe bone. Immediately ventral to the transverse ridge, on the internal surface of the bone, a large
opening leads directly into the facialis canal, and this opening transmits the ramus hyoideus, this
nerve thus never reaching the external surface of the hyomandibular. The remainder of the facialis
canal transmits the ramus mandibularis lateralis certainly accompanied by communis fibers, and
possibly also by certain general cutaneous fibers. The nerve so constituted is Joined, as it reaches
the outer surface of the bone, by a communicating general cutaneous bundle which arises from the

— a

trigeminus ganglion and issues through the trigeminus opening of the trigemino-facialis chamber,
this being the second trigeminus bundle to join the facialis, the other bundle issuing through
the facialis opening of the trigemino-facialis chamber, joining the nervus facialis internal to
the hyomandibular, and going largely, if not entirely, to the ramus hyoideus. The ramus
mandibularis, thus formed, after giving off certain branches, passes downward and inward through
a large opening between the hind edge of the sympleetie and the anterior edge of the web of bone
that spans the angle between the two limbs of the preopereular, this opening being the regular foramen
for the ramus mandibularis externus. Certain fibers other than lateralis ones form part of the nerve
that passes through the foramen, but whether they are partly communis or wholly general eutaneous
could not be determined in my material. It is, however, certain that, in this fish, no important
bundle of communis fibers passes inward anterior to the symplectic, where the ramus mandibularis
internus should normally pass, and, in my material, I could not there find an opening that I could
certainly call a foramen and not an artifact. From the facialis canal, near its internal opening, a canal
leads backward in the hyomandibular, as usual, opens on its external surface near its hind edge and
immediately ventral to the opercular process, and transmits a nerve containing lateralis and general
cutaneous fibers destined to innervate the dorsal two organs of the preopereular canal and tissues
on the outer surface of the opereular.

The ramus hyoideus facialis thus never reaches the external surface of the hyomandibular,
and it accordingly here has relations to that bone that might be taken to indicate that it was in process
of eutting through the bone from its outer to its inner surface; but this is certainly not the case, the
condition being in some way related to the development of that tall ridge on the external surface of
the bone that gives support to the preopereular. This ridge lies, in certain fishes (Scorpaena, Trigla ete.),
posterior to the external opening of the facialis canal through the hyomandibular, while in others
(Scomber) it lies anterior to that opening. If, in one of these latter fishes, the ridge were to be pushed
backward into the position, relative to the shank of the bone, that it has in Dactylopterus, it would
probably pass over the ramus mandibularis, held in position by its lower foramen, but would push
the ramus hyoideus downward and backward onto what would be morphologically a part of the
posterior surface of the bone, though appearing as a part of its internal surface. An intermediate
stage in such a process is shown in Gasterosteus, where, according to Swinnerton (02, p. 544), „the
hyomandibular nerve foramen occupies the same position as it did in the last stage, but externally
at first sight it seems to have disappeared; in reality it has been carried to the ventral edge [of the
hyomandibular] by overgrowth of bone“.

The distal end of that slightly thieckened portion of the hyomandibular that represents the
shank of the bone is in synchondrosis with the usual interspace of cartilage, that cartilage being
bounded anteriorly by the metapterygoid, antero-ventrally by the symplectie, and posteriorly by
the web of bone that fills the angle between the two limbs of the preopereular. The interspace gives
articulation, on its internal surface, to a relatively long and important interhyal. Immediately
dorsal to this interspace of cartilage, the anterior edge of the hyomandibular is in contact with and
firmly bound to the dorso-posterior corner of the metapterygoid, and between the two bones and
the interspace of cartilage there is a relatively large foramen which transmits the arteria hyoidea.

The SYMPLECTIC is broad and flat, and lies in the line, prolonged, of the shank of the hyo-
mandibular. Its ventral end overlaps the dorsal edge of the quadrate, and lies in a slight depression

on the internal surface of that bone. The anterior edge of the bone is bounded externally by the
Zoologica. Heft 57. 23

— [8 —

cartilage of the palato-quadrate apparatus, while internally it overlaps that cartilage and is in
contact with the hind edge of the metapterygoid. Its hind edge is in part in contact with the anterior
edge of the web of bone that spans the angle between the two limbs of the preopercular, and in part
is separated from that web of bone by a relatively large opening. This opening is spanned by mem-
brane, and the membrane is pierced by the arteria hyoidea and the ramus mandibularis externus
facialis, the lateralis fibers of that nerve being accompanied by general cutaneous ones and possibly
also by communis fibers, as just above explained. No mandibularis internus foramen, between the
symplectic and quadrate, could be found.

The METAPTERYGOID is a subcircular bone slightly concave on its internal surface. It
is bounded anteriorly by the entopterygoid, with which it is flexibly connected by tissue; ventrally
by the quadrate, from which it is separated by a narrow band of cartilage; and posteriorly by the
symplectie and the interspace of cartilage between the latter bone and the hyomandibular. A small
posterior process at the dorsal end of its hind edge is in contact with and bound by tissue to the
anterior edge of the ventral end of the hyomandibular, and this process is pierced by a foramen
which transmits the external carotid from the outer to the inner surface of the apparatus, the artery
there falling into the arteria hyoidea. In the ventral edge of the process there is a notch, which,
with the adjoining cartilage, forms a foramen which transmits the arteria hyoidea from the outer
to the inner surface of the apparatus. The process on the metapterygoid thus represents, as the hind
edge of the bone in Cottus does, the two flanges on the hind edge of the bone of Scorpaena.

The QUADRATE has a large posterior process, the thick and broad postero-ventral surface
of which rests against the dorsal surface of the ventral limb of the preopercular, the point of the
process passing into a pocket in that bone. The symplectic groove is simply a broad and shallow
depression on the internal surface of the dorsal edge of the bone, immediately anterior to this process.
Dorsally the bone is bounded by cartilage which separates it from the metapterygoid, and the anterior
edge of the bone forms, with that of the metapterygoid, a continuous line which is slightly convex
and lies in a nearly transverse position. The narrow band of cartilage that lies between the two
bones is prolonged a short distance beyond their anterior edges, there lies in a depression on the
external surface of the entopterygoid, and is exposed on the outer surface of the apparatus between
the ecto- and ento-pterygoids. The anterior edge of the quadrate overlaps internally the hind edge
of the ectopterygoid, but is itself overlapped internally by a short process at the ventral corner of
the latter bone, this latter process being in articular contact with the dorsal surface of the mesial
end of the articular head of the quadrate. The quadrate and ectopterygoid thus articulate in a measure
with each other, and as their adjoining edges are strongly but flexibly bound together by tissue, and
as the anterior edge of the metapterygoid is similarly bound to the hind edge of the entopterygoid,
a flexible joint is here formed in the hyomandibulo-palato-quadrate apparatus. The anterior pro-
longation of the band of cartilage that lies between the quadrate and metapterygoid crosses the
joint uninterruptedly, but being itself flexible does not interfere with the movements of the parts.
In the Cyprinidae, according to Sagemehl (’91, p. 582), the palato-quadrate apparatus is also jointed,
but in those fishes the joint is between the palatine and the ecto- and ento-pterygoids and hence
not similar to the joint in Dactylopterus.

The ECTOPTERYGOID is a stout elongated bone directed antero-dorsally. Its dorso-
anterior end suturates with the palatine, the two bones enclosing between them a palatine remnant

— 179 —

of the palato-quadrate cartilage. The dorsal edge of the bone overiaps externally and suturates
with the ventral edge of the entopterygoid, bounding, in its posterior portion, the short anterior pro-
longation of the palato-quadrate cartilage just above described. Its hind edge overlaps both extern-
ally and internally and artieulates with the anterior edge of the quadrate, in the manner just above
described. Near the ventro-posterior end of the free, ventral edge of the bone, there is a flat ridge-
like process, the function of which was not evident in my preparations.

The ENTOPTERYGOID is a relatively large, thin, sub-oval bone, the anterior end of which
overlaps internally the palatine, the ventral edge similarly overlapping the dorsal edge of the ecto-
pterygoid. Its hind edge is flexibly bound to the anterior edge of the metapterygoid. In a slight
depression on its outer surface, at its ventro-posterior corner, it lodges the short anterior prolongation
of the palato-quadrate cartilage.

The PALATINE is a stout irregular bone, with a short body, a right-angled maxillary process,
and a short ventral process the ventral edge of which is broadened and corrugated but bears no teeth.
The hind end of the bone suturates with the ectopterygoid and entopterygoid, being overlapped
externally by the former bone and internally by the latter. The three bones enclose between them
a small palatine remnant of the palato-quadrate cartilage, this cartilage not being exposed on the
outer surface of the apparatus. The maxillary process of the palatine is a stout process, the proximal
portion of which is directed antero-dorso-laterally and the distal portion antero-ventro-mesially,
the two parts lying nearly at a right angle to each other. The dorsal surface of the flat distal portion
of the process lies against, and has a sliding articulation with the internal surface of the lachrymo-
palatine process of the nasal bone, the ventral surface of the process giving articulation to, and being
firmly bound by fibrous tissue to, the dorsal surface of the maxillary bone. Immediately posterior
to the surface of contact with the nasal, the hind end of the flat dorsal surface of the maxillary process
has a sliding articulation with the two little articular ridges on the internal surface of the dorsal
edge of the lachrymal.

On the internal surface of the base of the maxillary process of the palatine, there is a V-shaped
groove which has a wide dorsal end and from there tapers gradually downward to a point. This
V-shaped groove articulates with the anterior edge of the lateral process of the vomer, and possibly
also with adjacent portions of the corresponding edge of the pedicle of the ectethmoid, in the manner
already described when describing those bones. Ventral to the groove there is, on the internal
surface of the anterior end of the ventral process of the palatine, a concavity which gives insertion
to the short vomero-palatine ligament and comes in contact with the lateral surface of the head of
the vomer when the palato-quadrate apparatus swings inward. The dorsal edge of the body of the
bone, and the dorsal edge of the entopterygoid immediately posterior to it, are both bound by strong
tissue to the ventral surface of the pedicle of the ectopterygoid, touching that bone when the palato-
quadrate apparatus swings inward.

The MANDIBLE contains dentary, articular and angular elements.

The dentary has the usual V-shaped hind end, the two limbs of the V being of about equal
length. The ventral limb tapers gradually to a point, and its hind end lies in a deep groove along
the internal surface of the articular. The dorsal limb of the bone is covered with small villiform teeth
and ends in a flattened hind end which replaces functionally the dorsal end of a coronoid process,
that process of the articular being wanting. On the external surface of the bone there is a deep groove

— 180° —

which doubtless lodges the anterior end of a gristly mandibular core, but this was not investigated
in the preparation of my material. On the ventral surface of the dorsal limb of the bone is inserted
the strong ligament that has its origin on the internal surfaces of the second and third infraorbital
bones. The bone is traversed by the mandibular latero-sensory canal and lodges but two sense organs
of the line.

The artieular is a stout bone with a pointed anterior end which fits into the V between the
two limbs of the dentary, lying on the dorsal surface of the ventral limb of that bone. On the ventral
half of its internal surface is a deep V-shaped groove which receives the hind end of the ventral limb
of the dentary. Near the hind end of this groove a canal traverses the bone from its ventral to its
dorsal surface, but what it transmits was not determined. The bone is without coronoid process,
and nearly its entire hind end is occupied by the articular facet for the quadrate. The bone is tra-
versed by the mandibular latero-sensory canal and lodges one organ of that line.

The angular is a small bone that fits against the ventral surface of the articular, there forming
a low, longitudinal and rounded ridge. At about the middle of its length there is a low transverse
ridge, the posterior surface of which gives insertion to a ligament that has its origin on a rod-like
bone that must represent the interopercular. From the hind end of this little bone a ligament extends
posteriorly and has its origin on the external surface of the dorsal ossification of the ceratohyal, near
its dorso-posterior end; the bone thus being intercalated in the mandibulo-hyoidean ligament, as a
part of that ligament, but seeming nevertheless to represent the interopercular.

The OPERCULAR is, as Gill has said, a flexible subtriangular bone, the external surface of
which is covered with scales.

The SUBOPERCULAR is said by Gill to be „almost membranous, mostly concealed“, and
to lie internal to the ventral end of the opercular. I find it as a relatively stout and curved bone,
the dorsal end of which lies internal to the ventral end of the opercular, while the ventral end
curves forward and lies against the internal surface of the preopereular; this latter end of the bone
being directed toward but widely separated from the hind end of the interopercular. In Figure 71,
which alone shows these bones, the line separating the subopercular and opereular has been omitted.

The INTEROPERCULAR is apparently represented, as Gill has stated and as just. above
described by me, by a rod-like bone intercalated in the mandibulo-hyoidean. ligament.

4, LATERO-SENSORY CANALS.

The main infraorbital canal begins at the dorsal edge of the lachrymal, directly antero-ventral
to the anterior end of the large nasal opening between the nasal and ectethmoid bones, there lying
directly opposite and close to the anterior opening of the supraorbital canal. It runs at first ventro-
laterally, then turns sharply backward at a right angle, and so continues in a nearly horizontal
position until it has traversed the lachrymal and the anterior two-thirds of the second infraorbital
bone. There it turns sharply upward and forward, at an acute angle, and curving backward and
upward borders the hind edge of the orbit, traversing the second, third, and fourth infraorbital bones.
At the anterior end of the horizontal part of its course, it sends a short branching tubule forward
in the lachrymal, and at the hind end of this part of its course, it sends a long branching tubule
direetly backward nearly to the postero-ventral corner of the second infraorbital bone. Numerous
other tubules arıse from the canal in this part of its course, some of them being simple tubes while

— 1831 —

others branch repeatedly, forming complicated dendritic systems. The tubules are scattered along
the canal instead of being grouped together, and it is impossible from the tubules alone to determine
the number of primary tubes. Furthermore, here, as in other parts of the latero-sensory system
of this fish, the large dendritic systems arise from the canals in the bodies of the related bones,
frequently near the middle point of the bone, and almost never in the sutural line between two
bones; this being distinetly a characteristic of the canals in the chondrostean ganoids, here found
in a teleostean fish. A full knowledge of the development of the system would accordingly be of
considerable interest.

The main infraorbital canal, having left the dorsal one of the infraorbital bones, enters and
traverses the postirontal, at the dorsal end of which bone it turns sharply backward and enters the
pterotie, anastomosing at the bend with what appears to be the terminal tube of the supraorbital
canal. The main infraorbital then traverses in succession the pterotice and suprascapular, lying for
a short distance, as it passes from one of these bones to the other, in a groove on the lateral edge
of the lateral extrascapular. It then traverses a short tubular bone that lies along the lateral edge
of the suprascapular and that apparently represents the latero-sensory component of the supraclav-
icular, as already set forth. As the canal traverses the pterotie it anastomoses with the dorsal
end of the preopercular canal, and as it traverses the lateral edge of the lateral extrascapular, it
gives off the supratemporal commissure.

In the main infraorbital canal there are three sense organs lodged in the lachrymal, two in the
second infraorbital bone, three in the third infraorbital and one in the fourth infraorbital, all inner-
vated by the ramus buccalis. In the postfrontal there is one organ innervated by the ramus oticus,
and in the pterotie three organs, two innervated by the oticus and one by the supratemporalis lateralis
vagi. In the section of canal that lies in the groove in the lateral extrascapular there is apparently
no organ, but the organ usually found here may be represented in a part of the one organ found in this
bone. This organ is unusually large, begins in the main canal, and from there extends postero-
mesially in the supratemporal commissure, thus certainly belonging, in part at least, to that commis-
sure. It is innervated by a single branch of the supratemporalis lateralis vagi. In the supra-
scapular there is one organ, innervated by the supratemporalis lateralis vagi.

The supratemporal canal begins at the lateral edge of the lateral extrascapular, opposite the
sutural ine between the pterotic and suprascapular, and running postero-mesially and then mesially
traverses the lateral extrascapular and then the mesial extrascapular, anastomosing, at the mesial
edge of the latter bone, with its fellow of the opposite side. Each of these two bones lodges a single
sense organ innervated by a branch of the supratemporalis lateralis vagi.

The supraorbital canal begins at the lateral edge of the single median nasal bone, and from
there runs upward and mesially, and then upward and backward in the nasal, eurving around the
anterior and then the mesial border of the large nasal opening of the skull. It then enters the anterior
edge of the frontal and runs almost directly backward to the middle point of that bone. There it
turns sharply laterally, and then curving laterally and backward reaches the postero-lateral edge of
the frontal, where it anastomoses, by what is apparently its terminal tube, with the main infraorbital
canal. In the full length of the canal there are, as in all the other fishes of the group, six sense
organs, one in the nasal and five in the frontal, all innervated by the ophthalmicus lateralis; but in
Daectylopterus the relations of the organs in the frontal to the frontal commissure are not as in those
other fishes. Here, three organs lie anterior to the commissure and two posterior to it, the commissure

— 12 —

accordingly being formed by what is, in its relations to the organs, the filth instead of the
fourth tube of the line. Furthermore, there is no primary tube between the first and second
frontal organs, and it is apparently the terminal tube of the line, instead of the penultimate tube,
that anastomoses with the main infraorbital canal.

The preopereulo-mandibular canal anastomoses by its dorsal end with the main infraorbital
as that canal traverses the pterotic. The canal traverses, as usual, the preopercular, articular and
dentary, the former bone lodging six sense organs, the articular lodging one organ, and the dentary
two organs; all innervated by the mandibularis externus facialis.

II. THE MYODOME.

Having found a myodome in Dactylopterus, in which fish it is said by Gill ('88) and other
authors to be wholly wanting, I have been led to look up, as fully as the literature and material at
my disposal would permit, all other teleosts in which this canal is also said to be absent. Before
discussing these other teleosts it is, however, necessary to quite fully describe the related conditions
in Lepidosteus; for a proper understanding of the conditions in that fish, already briefly described
by Sagemehl, is most important in this connection.

Of Lepidosteus Sagemehl says (’S4b, p. 86); „Bei Lepidosteus wird durch besondere Fortsätze
der Petrosa ein nach vorn gegen die Schädelhöhle geöffneter Halbkanal gebildet, der dicht hinter der
Hypophyse von einer Seite zur anderen verläuft und nach vorn, also gegen die Hypophyse hin, durch
eine Membran vollständig abgeschlossen und zu einem allseitig gedeckten Querkanal verwandelt
wird, welcher von lockerem Fettgewebe erfüllt ist. Lateral reicht dieser an der Basis eranii dicht
hinter der Hypophyse verlaufende Kanal bis an den hinteren, unteren Winkel der Orbita, nach welcher
hin er vollständig verschlossen erscheint. Abgesehen von dem letzteren Umstande besitzt dieser
Raum genau dieselben Verhältnisse, wie der von Gegenbaur beschriebene Canalis transversus der
Selachier; der Verschluß gegen die Orbitae ist wohl ein sekundärer. Auf der anderen Seite kann es
eben so wenig einem Zweifel unterliegen, daß dieses der Augenmuskelkanal von Amia ist, wenn man
die hier gegebene Beschreibung mit der Fig. 7 meiner Arbeit über Amia vergleicht, wo der unter dem
horizontalen Fortsatz des Petrosum und vor demselben gelegene durch eine Fascie (die nicht ab-
gebildet ist) zugedeckte Raum von dem Rectus externus eingenommen wird. Die von Gegenbaur
vertretene Hypothese kann somit durch weitere Tatsachen gestützt werden.“

In the adult Lepidosteus the brain case, in the region of the pituitary body, is somewhat more
than twice as wide as it is tall. In a 19 mm embryo these two dimensions, in this same region, are
nearly equal. There is thus, in this region, a flattening of the brain case as the fish develops, and
this flattening process seems to particularly affect the ventral portion of the brain case. Because
of it, the ascending processes of the parasphenoid of the adult are flat plates, projeeting almost directly
laterally from the body of the bone. Their lines of origin from the body of the bone incline back-
ward and slightly upward, the two processes thus lying practically in the same plane, and that plane
being a transverse one that inclines but slightly upward and backward to the axis of the parasphenoid.
Each process is, in extent and position, the equivalent of the ascending process of Parker’s (°82b)
figures of young Lepidostei fused with the so-called alisphenoid bone of those same figures, Parker
showing these latter bones as separate and independent ones in 2 and 4 inch larvae and describing
them as such in the adult.

— 14 —

In larvae 55 and 80 mm in length, I find, oceupying the place of the alisphenoid bone of
Parker’s descriptions, a V-shaped process of the parasphenoid which embraces the mesial edge of an
anterior plate-like process of the proötie cartilage. This process of the proötie cartilage occupies the
place of, and certainly is the basipterygoid process of Parker’s descriptions, but it has a short free
mesial edge not shown by Parker. The anterior edge of the V-shaped process of the parasphenoid
is closed by a rounded union of the plates that form its two limbs, and the limbs are here both
short, extending laterally only about one third the width of the cartilage. This rounded anterior
edge of the process, and the corresponding edge of the cartilage beyond it, together, give articulation
to the metapterygoid. The point of the V 'of the V-shaped process is directed mesially toward the
lateral edge of the parasphenoid, but it does not, in its anterior portion, quite reach that edge.
Posteriorly it meets and fuses with the edge of the parasphenoid, thus becoming a part of the
ascending process of that bone. The dorsal (internal) limb of the V there vanishes, while the
ventral (external) liimb becomes prolonged into that tall plate of the ascending process of the
parasphenoid that lies against the external surface of the proötic cartilage. In 19 mm and 25 mm
specimens, which I have also examined, the internal limb of the V-shaped process has not yet
developed, the external limb alone being found. The V-shaped process of older specimens is
thus, in these young larvae, simply a plate-like part of the ascending process of the parasphenoid
which, projecting forward, forms the lateral boundary of a narrow space, or notch, between itself
and the lateral edge of the body of the parasphenoid. Through this notch the efferent pseudobranch-
ial artery runs upward, and then turns mesially between the body of the parasphenoid and the
overlying cartilaginous basis cranii, to join and completely fuse with the internal carotid. Im-
mediately posterior to the notch, the ventro-mesial edge of the base of the basipterygoid process
of the proötie cartilage fuses with the ventral surface of the lateral edge of a short band-like portion
of the cartilage of the region, this latter cartilage bounding the space in which the hypophysis lies.
Posteriorly this band is continuous with the parachordal cartilage, while anteriorly the lateral end
of its nearly straight anterior edge is continuous with the thickened ventral edge of the cartilage
of the alisphenoid region; that thickened edge of the alisphenoid cartilage being continuous, anter-
iorly, with the hind end of a median portion of the trabeeular cartilage. Whether the short band
of cartilage is of trabeeular origin, or not, I can not positively tell, but it would seem as if the
trabecular cartilage could not extend posteriorly, on either side, beyond the hind end of the
thickened ventral edge of the alisphenoid cartilage. This being the case, the short band of cartilage
would represent the anterior end of the parachordal cartilage, and as such I consider it; the hypo-
physis then lying between the anterior ends of the parachordal cartilages. Parker shows this part
of the chondrocranium of Lepidosteus somewhat different from what I find it, and he considers the
cartilage of this region as of trabecular origin; but he also considers the basipterygoid process as
of trabecular origin, and that cartilage, being a process of the proötie cartilage, must certainly be of
post-trabecular origin.

The basipterygoid process of Lepidosteus, it may here be stated, has so closely the position
and the relations to the nerves and blood vessels of the region that the basipterygoid process of
Lacerta has (Gaupp, ’00, p. 537), that it must be the homologue of that process. In Amia, it is
apparently represented in the little cartilaginous process that is perforated by the efferent pseudo-
branchial artery (Allis, 97a), and that rises from the lateral edge of what is apparently the hind
end of the fused trabeculae. In most teleosts the process seems wholly wanting.

— 185 —

Parker’s alisphenoid bone is thus, as I find it, even in 55 mm specimens, simply a part of the
ascending process of the parasphenoid, and I am unable to explain how Parker could have found it,
separate and independent, not only in a 2 inch (50 mm) but also in a 4 inch (100 mm) specimen.
Parker furthermore states that his alisphenoid is an endosteal bone. In my 55 mm and 80 mm
embryos the corresponding basipterygoid process of the parasphenoid is, in its anterior portion,
surrounded by dense tissue the character and origin of which I am unable to determine, not being
sufficiently versed in the subject; but it would seem to result, in part, from the breaking down of the
superficial layers of the cartilage against which the bone lies. In the 19 mm and 25 mm specimens this
dense tissue is already being developed, but at these ages the tissue lies almost entirely between the
bone and the cartilage, and it may accordingly be wholly of perichondrial origin. Whatever its origin,
this part of the parasphenoid certainly has relations to the underlying cartilage somewhat different
from those of the other portions of the bone, and it would seem to be a typical case of a dermal bone
in process of acquiring primary relations to an underlying cartilage. It is, however, to be noted
that perichondrial bone has nowhere else appeared, in the earliest of the stages examined, and that
when it does appear it is not imbedded in dense formative tissues, as the bone here in question is.
In the adult this part of the ascending process of the parasphenoid certainly has much the appearance
of perichondrial bone; but it runs insensibly into the posterior portion of the process, where both
plates of the V-shaped portion of the bone are certainly of ectosteal origin, for they both extend
beyond the dorso-lateral edge of the cartilage they enclose, and there overlap, superficially, portions
of the inner and outer surfaces of the ventro-mesial edge of the proötie bone. But, whatever its
origin, this part of the parasphenoid is certainly not the alisphenoid, for that bone is found elsewhere,
in its proper place, as a wholly independent ossification.

In the adult, on the anterior edge of the basipterygoid portion of the ascending process of the
parasphenoid, there is a tit-like process which projects toward and sometimes even abuts firmly
against the lateral surface of the body of the parasphenoid slightly anterior to the base of its ascending
process. This little process lies in a horizontal position, at right angles to the axis of the parasphenoid,
and between it and the anterior edge of the basal portion of the ascending process there is a more
or less completely closed opening which transmits the eflerent pseudobranchial artery. The anterior
edge of the tit-like process is straight and forms part of the artieular surface for the metapterygoid,
the remainder of that artieular surface being formed by the straight anterior edge of the basipterygoid
process and a corresponding edge of that part of the proötie cartilage that lies dorso-lateral to the
process. This little tit-like process is thus a mesial growth of the anterior end of the V-shaped part
of the bone of embryos, and it is to be remarked that, although it may abut firmly against the body
of the parasphenoid, I have never found it fused with that bone. It is not shown in any of Parker’s
figures, but the general arrangement of the parts can be readily understood by reference to those figures.

Between the proötic bone and the hind edge of the external plate of the ascending process
of the parasphenoid, there is an opening which leads into a short canal between the parasphenoid
and the overlying cartilage of the basis cranii, the opening thus having exactly the position of the
internal carotid foramen of Amia and teleosts, and unquestionably being the homologue of that
foramen. In Lepidosteus, however, this foramen transmits the common carotid, which artery,
immediately within the foramen, separates into its external and internal branches. The external
carotid, turning upward, traverses a foramen that perforates the ventro-mesial edge of the proötie,
but lies partly in that bone and partly in the cartilage that bounds it. The artery then runs upward

Zoologiea. Heft 57. 24

— 186 —

and backward in a deep groove that lies on the orbital surface of the proötic and that leads into a
large trigemino-facialis chamber. This groove, in Lepidosteus, transmits the ramus palatinus
facialis as well as the external carotid artery, the nerve traversing the foramen in the proötie with
the artery, and entering the carotid canal. This foramen in the proötic of Lepidosteus is accordingly
the homologue of the palatinus and external carotid foramina of Amia, coalesced into a single opening.
It has closely the position of the palatinus foramen of Amia, and neither it nor the carotid foramen
are shown by Parker in any of his figures.

In sections of embryos, a delicate pharyngeal branch of the glossopharyngeus is found accom-
panying the common carotid artery, and although it could not be traced as far as the carotid foramen,
it doubtless traverses that foramen, with the artery, as in Amia.

The internal carotid artery, having separated from the external carotid immediately beneath
the palatinus foramen, runs forward in a canal between the cartilage of the basis cranii and the under-
lying parasphenoid, lying in a slight groove on the dorsal surface of the latter bone. It is accom-
panied, in this canal, by the ramus palatinus facialis and probably also by the delicate branch of the
glossopharyngeus just above described. Having arrived near the anterior edge of the ascending
process of the parasphenoid, and there lying anterior to the pituitary fossa, the internal carotid
receives the efferent pseudobranchial artery. It then, in all my embryos, immediately separates
into two parts. In the smaller embryos, these two parts both turn upward and traverse the inter-
trabecular space, while in the older embryos, they perforate the overlying cartilage and so enter
the cranial cavity, one part traversing a large foramen and the other traversing a small and imper-
fectly enclosed branch canal which leads from that foramen. The larger one of these two branches
gives off several intracranial branches and then leaves the cranial cavity with the nervus opticus.
The smaller branch also issues with tbe opticus, but it gives off no perceptible branches during its
intracranial course, and it may perhaps be reminiscent of the otherwise wholly wanting anterior
continuation of the efferent pseudobranchial artery. Shortly before the anastomosis with the efierent
pseudobranchial artery, the internal carotid gives off a small branch which runs forward, accompanying
the palatinus facialis, in an anterior prolongation of the canal between the parasphenoid and the
overlying cartilage of the base of the skull. This latter artery and the two carotids are all three briefly
mentioned by Wrisht (’85) in his description of the arterial circulation in embryos of Lepidosteus,
but their foramina and their courses relative to the cranium are not well or sufficiently given by him.

In the adult, the trabeculae of opposite sides have fused with each other in the middle
line, and the internal carotids traverse foramina in the basis cranii, these foramina corresponding to
the internal carotid canals of my descriptions of Amia (°97). Slightly anterior to these canals there is
a shallow transverse groove across the dorsal surface of the fused trabeculae, this groove corresponding
exactly, in position, to the canalis transversus of my descriptions of Amia, and being quite undoubt-
edly the homologue of that canal. The groove is, however, not the homologue of the canalis trans-
versus of selachians, as I have pointed out in a later work (’01), and the selection of the name, in my
descriptions of Amia, was unfortunate. The groove, in Lepidosteus, forms the anterior boundary
of a slightly raised portion of the cartilage of the basis cranii, which extends backward to the anterior
edge of the pituitary fossa and is the homologue of the much more pronounced transverse prepituitary
bolster of Amia.

The pseudobranchial artery, in Amia, does not itself fuse with the internal carotid, a small
communicating branch, only, which perforates a lateral projection of the basis cranii, uniting the

— Il —

two arteries. In Lepidosteus, it is the main efferent pseudobranchial artery, itself, that here unites
with the internal carotid, traversing, to reach that artery, the imperfeetly closed foramen in the
anterior edge of the ascending process of the parasphenoid. This difference in this artery, in these
two fishes, is doubtless due to the absence of a choroid gland in Lepidosteus; that orbital continuation
of the artery that supplies that gland in Amia naturally being suppressed with the gland, in Lepi-
dosteus, and the communicating branch of Amia becoming, in Lepidosteus, the direct anterior continua-
tion of the main artery.

The palatinus facialis and external carotid of Lepidosteus run upward and backward, as
already stated, in a groove that leads into a trigemino-facialis chamber in the proötic. This chamber
has a very large trigeminus, and a smaller facialis opening, and its bony mesial wall is a direct posterior
continuation of the bony wall that encloses the anterior part of the cranial cavity; Lepidosteus, in
this, resembling Scomber and the mail-cheeked fishes, and differing markedly from Amia. The mesial
wall of the chamber is perforated by a single large foramen for the roots of the trigemino-facialis
nerves, two small processes representing the beginnings of a separation ofthe foramen into two or more
parts. Slightly antero-ventral to this foramen the anterior edge of the proötic is perforated by another
foramen, the anterior border of which is formed by a small flat bar of cartilage which, rising from
the trabecular cartilage and extending upward to the ventral edge of the alisphenoid, separates the
foramen from the ventral portion of the optic fenestra. This foramen transmits the pituitary vein,
which vein arises beneath the hypophysis, in direct communication with its fellow of the opposite
side, and from there runs dorso-antero-laterally to traverse its foramen and fall into the (internal ?)
jugular slishtly posterior to the point where that vein is joined by the orbito-nasal vein. The pitui-
tary vein receives a small branch, on either side, from the cross-canal of Sagemehl’s descriptions,
these branches being traced in sections and not in the adult. The vein, in the adult, lies, in its intra-
cranial course, beneath a mass of fatty tissue which covers the floor of the cranial cavity, and this
fatty tissue in the cranial cavity of the skull of fishes is said by Sagemehl (’S4a) to lie between inner and
outer limiting membranes which are parts of the dura mater. Some part of this tissue, in Lepidosteus,
is accordingly the homologue of the tough glistening membrane that, in Amia, forms not only the roof
of the anterior portion of the myodome, but also the mesial wall of the trigemino-facialis chamber
of that fish. The foramen that transmits the pituitary vein, in Lepidosteus, is thus quite certainly
the equivalent of some part of the ventral portion of the orbital opening of the myodome of Amia,

Immediately dorsal to the foramen for the pituitary vein, between the adjoining edges of the
proötic and alisphenoid, there is another foramen, which transmits the nervus oculomotorius and
probably the radix profundi also, for although this latter nerve, in my 80 mm specimen, pierces the
cartilaginous cranial wall close to but wholly separate from the oculomotorius, I do not find a separate
foramen in the one adult skull that I have examined in this connection. Van Wijhe (’82) says that
he found the profundus issuing by a separate and independent foramen. Somewhat dorsal to these
two foramina, in the sections of my SO mm specimen, the trochlearis pierces the cranial wall, and,
slightly posterior to that nerve, the wall is perforated by a branch of the orbito-nasal vein. These
two latter foramina are, one or both, represented, in my adult specimen, in a short canal that tra-
verses the alisphenoid slightly dorsal to the oculomotorius foramen.

Stannius (’49, p. 19) says that, according to Müller, the oculomotorius, trochlearis and trige-
minus of Lepidosteus all issue through a single large foramen in the „Keilbeinflügel”’; a statement
that is certainly not wholly correct.

= ]j88 —

A short leg of the alisphenoid forms, in the adult, the anterior boundary of the oculomotorius
foramen, the ventral end of the leg being continuous with the small flat bar of cartilage that lies
between the ventral portion of the optie fenestra and the foramen for the pituitary vein; and as this
bar of cartilage rises from the lateral edge of the basisphenoid region of the trabecular cartilage, the
associated leg of the alisphenoid must be the basisphenoid leg of that bone. ‘Of the parasphenoid
leg of the alisphenoid I can find no trace, the alisphenoid of Lepidosteus thus being strietly of the
usual teleostean type.

The recti muscles of the eye all have their origins from the skull immediately ventral and
posterior to the optic fenestra, and hence in the immediate neighbourhood of the foramen for the
pituitary vein. The rectus externus, in the 80 mm specimen, separates into two portions as it ap-
proaches the skull, and the tendon of one of these portions traverses the foramen with the vein, and,
following it, has its origin beneath it; but whether its point of origin is on the cartilage of the-basis
eranii, on the parasphenoid, or in fibrous tissue of the region, I could not determine.

Although wholly unrelated to the present subject, it may here be stated that the rectus in-
ternus arises, in Lepidosteus, by a long and slender tendon which is closely applied to the antero-
mesial surface of the reetus inferior, these two muscles thus arising as a single muscle and being,
practically, not yet fully differentiated parts of a single muscle; this being in accord with my suppos-
ition (97a) that these two muscles of teleosts and bony ganoids arise by the splitting of the single
rectus inferior of elasmobranchs. These two muscles, and the reetus superior and obliquus inferior,
are innervated by the oculomotorius in the manner and order that they are in Amia, this confirming
my interpretation (97a, p. 520) of Van Wijhe’s description of this fish. The abducens leaves the
eranial cavity through the trigemino-facialis foramen, piereing the membrane that closes that foramen
antero-ventral to and independent of the trigemino-facialis roots. It then runs antero-laterally, vent-
ral to the jugular vein, between it and the external carotid, lying internal and antero-internal to
the ventral edge of the trigemino-facialis ganglion, and reaches the rectus externus. It does not
pass over the truncus trigeminus, as stated by Schneider (°81), but, as the reetus externus passes
over that truncus, the abducens naturally also would, if it were sufficiently prolonged. The radıx
profundi, after its exit from the skull, enters an extra-cranial profundus ganglion which lies close
against the side wall of the skull immediately dorso external to and in contact with the oculomo-
torius, and not below that nerve, as shown by Schneider. Two ventral or ventro-anterior prolong-
ations of the ganglion terminate in small ganglionie swellings, which lie in contact with the inferior
branch of the oculomotorius and are the ciliary ganglia. From the anterior end of the profundus
ganglion a stout portio ophthalmiei profundi arises. The trigemino-facialis ganglion lies, as in Amia,
wholly outside the cavum cranii, a few scattered cells only being found in the roots of the nerves.

The cross-canal of Sagemehl’s desceriptions can now be considered. The enclosing walls of
this canal form, in the fresh skull of the adult fish, a prominent transverse bolster on the floor of
the eranial cavity, and this bolster must quite unquestionably have arisen by the depression of the
anterior edge of the proötic bridge of a fish like Amia (Allis, °97a, Fig. 11) or Polypterus (Pollard,
’92, Fig. 12) until it met and then fused with the floor of the eranial cavity on either side of the
saccus vasculosus. The cross-canal of Lepidosteus is thus a strietly intramural space that
lies beneath a proötie bridge of the primary type found in Amia, and that is related either primarily
or secondarily to the saccus vasculosus. This space represents the posterior half only of the myo-
dome of Amia, and it might have been developed either from the conditions found in that fish, which

— 189

has a myodome, or from those found in Polypterus which has no myodome. In Lepidosteus the
mesial processes of the proötics, which unite to form the proötie bridge, are said by Sagemehl to be
connected, across the median line, by membrane, instead of by cartilage. To me this connecting
tissue looks much more like cartilage or fibro-cartilage than like membrane, but this is unimportant,
for even in Amia membrane is here first formed and later chondrifies. Sagemehl further says that
this membrane entirely closes the canal toward the cranial cavity. This is an error, for I find the
anterior wall of the canal always perforated by a median oval opening through which the apparently
short saccus vasculosus projects. The cross-canal is filled, as Sagemehl states, with a mass of fatty
tissue and this tissue is richly supplied with blood.

Immediately anterior to the cross-canal there is, in the floor of the cranial cavity, the pit-
like and slightly oval pituitary fossa. The lateral and anterior walls of this fossa are of cartilage.
The floor of the fossa is perforated by a nearly circular opening, the opening being closed ventrally
by the parasphenoid. Posterior to this circular opening, and extending to or slightly beyond the
anterior wall of the cross-canal, the floor of the pit is, in my medium-sized adults, formed of tough
membrane only. Posterior to this membrane the floor of the eross-canal is of cartilage, and inclines
gradually and slightly upward to the base of the ridge of cartilage that forms the posterior boundary
of the cross-canal. The circular opening in the cranial floor is accordingly the hypophysial fenestra,
the greatly reduced pituitary space, or pituitary fenestra of Parker’s descriptions of embryos of
Lepidosteus, and this fenestra of the adult Lepidosteus is the striet, but reduced homologue of the
hypophysial fenestra of Amia. The fenestra of Lepidosteus is said by Parker to lie between the
„‚roots““ of the trabeculae; but, as already stated, the laterally bounding cartilages seem to me to
be the anterior ends of the parachordal cartilages. Parker’s opinion was doubtless based; Ist., on
the position of the hypophysis, in early embryos, between the hind ends of the trabeculae; and, 2nd.
on the position of the posterior clinoid bridge of his descriptions, which bridge is said by him (l. ce.
p. 481) to run „straight across, joining the roots of the trabeculae together‘. But, this posterior
clinoid bridge simply represents an early stage in the development of the enclosing walls of Sage-
mehl’s cross-canal, and hence joins regions of parachordal and not of trabecular origin. Furthermore,
the position of the hypophysis in earlyembryos need not necessarily be the same as that in the adult.
For, the intertrabecular and interparachordal fenestrae of early embryos being continuous, as shown
by Parker, the well-known unequal longitudinal growth of the cartilage of the basis cranii and the
overlying brain might easily pull the pituitary body backward, out of the hind end of the inter-
trabecular space into the interparachordal region. And this, in my opinion, has certainly taken place
in Lepidosteus.

Sagemehl says that the lateral ends of the cross-canal closely approach the postero-ventral
corner of the orbit. This is an error, for the cross-canal is everywhere widely separated from the orbit.
He further says that the cross-canal exactly resembles the canalis transversus of selachians, excepting
that it is closed toward the orbit. This also is not wholly correct, for as the canalis transversus of
selachians is traversed (Allis, ’Ol) by a venous sinus and not simply by a Iymph sinus, as Sagemehl
supposed, it must be represented, in part at least, in Lepidosteus, by the canal that transmits the
pituitary vein. There are here, in fact, two spaces that would seem to be of separate and independent
origin; one a median space that is either primarily or secondarily related to the saccus vasculosus, and
the other a canal that leads from the orbit, on either side, and is traversed by the pituitary vein. The
sacculaf space is roofed by the mesial processes of the proötics, and from it, or immediately in front

— 190 —

of it, the canal for the pituitary vein leads on either side into the orbit, lying ventral and then lateral,
or antero-lateral to the hypophysis.

The conditions in Lepidosteus thus all indicate that the myodome of Amia would arise if certain
of the recti muscles of the former should force an entrance into the cranial cavity, and then into
the saccular space, traversing, in this process, the foramen and then the canal for the pituitary vein.
The recti muscles, as already stated, already have their origins in the immediate vieinity of the foramen
for the vein, and one head of the rectus externus has, in my 80 mm specimen, already acquired a very
considerably intracranial extension. If this head of this muscle were to continue its progress, at the
same time increasing largely in size, it would, following the vein, make its way backward between
the cartilaginous floor of the cranial cavity and the overlying membrane, would force that membrane
and the overlying brain upward in the cranial cavity, and might finally reach and break down the
anterior wall of the eross-canal; the myodome of Amia thus being produced. And this is, in principle,
the manner in which Sagemehl suggests that the teleostean myodome did arise, although in the details
ol his explanation he is wrong. The conditions in Lepidosteus might however represent a stage
in the abortion of the conditions that preceded and led to the establishment of a myodome, those
pre-existing conditions being represented in Polypterus; and this seems to me the proper interpretation
of the facts, as wıll be later discussed.

But, whatever the origin of the myodome, there are in Lepidosteus, as there are in Amia and
Scorpaena, two floors in the pituitary region of the cranial cavity, the dorsal one of these two floors
being membranous to a different extent in each of these three fishes. The lateral walls of this part
of the skull are also double in each of these three fishes, one or the other of the two walls being
also membranous to a different extent in each of the fishes. In the space between the two floors
lies the myodome, either actual or potential, while in the space between the two lateral walls lies
the trigemino-facialis chamber. In Dactylopterus the conditions are modified and obscured by
the fact that the dorsal floor arises from or near the anterior edge of the ventral floor and is inclined
at a marked angle to it.

According to Starks (°05), the ventral floor of the myodome of fishes ‚‚is the true cranial base“,
the dorsal floor being simply a septum of secondary development; and the conditions that I have
described in Amia would seem to favor this interpretation, the dorsal wall of the myodome chondri-
fying, in that fish, much later than the ventral wall. But this condition is not invariable in fishes,
as Handrick’s (°01) descriptions of Argyropelecus show. In that fish the myodome is said to begin
beneath the membranous pituitary fossa, and from there to extend backward immediately beneath
the cartilaginous floor of the cranium until it reaches and ends against the „‚anterior outer wall‘ of
the bulla that encloses the sacculi and lagenae. The side walls and floor of this myodome are not
particularly described, but they are evidently formed by portions of the hard, modified, connective-
tissue membrane that is said to largely cover the roof and side walls of the cartilaginous eranium,
and the trigemino-facialis chamber of either side would seem to be in direct communication with the
myodome, as it is in Amia. The trigeminus ganglion is said to be an extracranial one, and to lie
in the upper corner of the myodome, The ciliary ganglion is also said to lie in the myodome, while the
sympathetie ganglion is said to lie on the outside of the side wall of the myodome, and the communis
and lateralis ganglia of the V—VII complex, which evidently form thelargeso-called facialis ganglion,
to lie entirely within the cartilaginous cranium. The cartilaginous wall of the cranium is said to
be perforated, on either side, by three separate foramina, one of which transmits the nervus oeculo-

— 11 —

motorius, a second the root of the trigeminus accompanied by a single trunk from which arise the
ophthalmieus and buccalis lateralis, and a third the truncus facialis accompanied by the palatinus
facialis and nervus abducens. The root of the trigeminus evidently includes the radix profundi,
but whether the ganglion of that nerve is intracranial or extracranial is not evident. It is however
plainly evident that the cartilaginous floor of the cranium, immediately posterior to the pituitary
fossa, is a proötic bridge, and that the side wall of the cranium on either side of the pituitary region
represents the inner wall of the trigemino-facialis chamber, the outer wall of that chamber, and also
the ventral wall of the myodome, being wholly of membrane.

It is thus evident that no positive conclusion can be formed as to which one of the two floors
of this part of the skull of fishes is the primary, and which the secondary one, until it is first known
what parts of the membranes here concerned belong to the primordial membranous capsule of the
brain and what parts, if any, are developed independently, internal to that capsule, as protective
coverings to the brain. The myodome, as it actually exists, is however certainly a space in the dura
mater, as that membrane is defined by Sagemehl in his descriptions of Amia, and as both its inner
and its outer walls may in large part chondrify or ossify as parts of the cranial wall, the myodome
is an intramural and not an intracranial space. This I have already stated in an earlier work (’97b,
p- 10), there speaking of the myodome as an intracranial space, but qualifying this by saying that
it is „a space that certainly lies morphologically in, and not internal to, the membranous bounding
walls of the primordial skull“.

In the labyrinth region also, both the ventral and the lateral walls of the skull of fishes are
partly double, the sacculi of the membranous ear lying between the two ventral walls and the semi-
circular canals between the lateral walls. The inner one of these two walls is largely membranous
in teleosts and the bony ganoids, but it may partly ossify as the mesial processes of the exoccipitals.
In elasmobranchs the wall may be largely of cartilage.

In most prepared skulls these two walls of the skull of fishes are not apparent, for their mem-
branous portions can only be preserved in careful preparations, and are almost always entirely
removed. In serial sections of embryos, also, particularly of early embryos, the membranous portions
of these walls are apt not to be recognized as such. Yet the fact that they both exist must always
be carefully borne in mind, for it, alone, permits of a proper comparison of this region, not only of
fishes with one another but of fishes with higher vertebrates.

In the chondrocranium of embryos of Lacerta agilis the hypophysis lies, according to Gaupp
(00, p. 470), in a hypophysial fenestra bounded laterally by the diverging hind ends of the trabeculae,
and posteriorly by a transverse bar of parachordal cartilage, called by Gaupp the crista sellaris. This
crista sellaris unites the anterior ends of the parachordal plates, and separates the interparachordal
fontanelle from the intertrabecular fontanelle, or hypophysial fenestra; thus having approximately,
if not exactly, the position of the posterior clinoid bridge of Parker’s deseriptions of Lepidosteus. The
carotis cerebralis, on either side, traverses, in early stages, the postero-lateral corner of the hypo-
physial fenestra, but in later stages it becomes entirely enclosed in cartilage, in an independent carotid
foramen. Slightly anterior to the hypophysial fenestra lies the subieulum infundibuli, a V-shaped
cartilaginous plate that rises from the hind edge of the interorbital septum. Anteriorly, this plate
of cartilage forms part of the hind border of the optie fenestra, while posteriorly it gives support
to the anterior border of the lobus infundibularis. The V-shaped plate of cartilage thus has strikingly
the position of the basisphenoid cartilage of Scorpaena, and this latter cartilage has been shown

to be the homologue of the transverse prepituitary bolster of Amia. The lateral edge of the plate,
in Lacerta, is connected, on either side, by the pila metoptica, with the taenia parietalis media, this
latter structure being a horizontal bar of cartilage that forms part of the side wall of the cranial cavity.
The pila metoptica forms part of the anterior boundary of the fenestra metoptica, which transmits
the oculomotorius and trochlearis nerves; those nerves thus undoubtedly running forward lateral
to the pila metoptica, into the orbit. The cartilaginous pila metoptica of Lacerta thus corresponds,
in its relations to these two nerves, to the basisphenoid leg of the alisphenoid bone of Lepidosteus,
and to the fibrous tissue that, in Amia, represent the same leg and forms the mesial boundary of the
tall orbital opening of the myodome. In Amia, the relations of the two nerves to the basisphenoid
leg of the alisphenoid are not positively indicated, that leg being represented by an undefined
portion of a continuous membrane. In teleosts, the oculomotorius issues, in all the fishes I have
examined, posterior to the sutural connection of the alisphenoid with the basisphenoid, and
hence lies posterior to the basisphenoid leg of the alisphenoid. The trochlearis has however
in teleosts the same indefinite relations to the basisphenoid leg of the alisphenoid that it has
in Amia, for it issues along the ventral or ventro-anterior edge of the alisphenoid, but anterior
to the sutural connection of that bone with the basisphenoid. It must accordingly either lie
anterior to the basisphenoid leg of the bone, or perforate an unossified portion of that leg; probably
the latter.

In Lacerta the hypophysis lies posterior to the subiculum infundibuli, between it and the
crista sellaris. Lateral to the crista sellaris, the nervus abducens pierces the basal parachordal plate,
near its anterior edge, and, running forward in the plate, opens on its very edge; the foramen not
being shown in ventral views. From there the nerve must run forward dorsal to the trabeculae,
as it does in the Frog (Gaupp, ’93a) and Necturus (Platt, ’97), and in this part of its course it must
lie between the trabeculae and an overlying membrane of some kind, doubtless a somewhat differ-
entiated layer of the dura mater. This membrane would certainly underlie the hypophysis and so
represent a membranous floor of this part of the cranial cavity, but to what extent it is developed
or differentiated, I can not determine from the literature at my disposal. Assume it to be well devel-
oped. It would extend between the subiculum infundibuli and the crista sellaris, forming a mem-
branous fossa around the hypophysis, and leaving a space between itself and the underlying cartilage
of the skull. This space must be traversed by the vein that is said by Gaupp (’93b, p. 571) to run
forward from the hypophysis into the orbit, and which is the evident homologue of the pituitary
vein of my descriptions of Amia, Lepidosteus and Scorpaena. The space must, furthermore, be
traversed by the carotid artery, which artery having either traversed the hypophysial fenestra or
a closely adjoining and independent foramen, is said by Gaupp (l. c. p. 571) to run forward close
to the brain; thus doubtless passing dorsal to the subiculum infundibuli. These conditions in Lacerta
are thus all too similar to those in the fishes referred to not to warrant the following conclusions:
(1) that the cartilaginous floor of the cranial cavity of Lacerta is probably the homologue of the
ventral floor of the myodome of fishes; (2) that there is, in the pituitary region of this skull, and
dorsal to the cartilaginous floor, a space of uncertain dimensions which corresponds to a part, if not
to the whole, of the myodome of fishes; (3) that the hypophysial fenestra of Lacerta is consequently
the striet homologue of the hypophysial fenestra of Lepidosteus; and (4) that the subiculum infundi-
buli is the homologue of the basisphenoid cartilage of Scorpaena, and hence of the transverse pre-
pituitary bolster of Amia.

— 193 —

With the human skull I have already attempted, in an earlier work (°97b), to compare the
condition found in Amia, and certain conclusions there arrived at can be repeated here with additional
facts in their support.

In Man (Quain ’92/96), the Gasserian ganglion lies in the cavum Meckelii, that cavum being said

to be a recess in the dura mater which occupies a depression on the upper surface of the petrous
portion of the temporal bone. But this so-called recess must be a space in the dura mater and not
a simple recess on its cerebral surface; for elsewhere in the same work the Gasserian ganglion is said
to lie between the inner and outer layers of the dura, the inner one of these two layers being the
primitive, single-layered dura, and the outer one being the endocranium, or internal periosteal mem-
brane of the skull. The fusion of these two separate membranes of embryos is said to form the double-
layered dura of the adult, the Gasserian ganglion being, in this process, enclosed between the two
layers. The internal part of the cavum Meckelii is said to come into close relations with the posterior
extremity of the cavernous sinus, that sinus also being a space between the two layers of the dura
of the adult, and the sinuses of opposite sides being in communication by means of the intercavernous
sinuses. Between the cavernous sinuses of opposite sides, in a median depression on the dorsal sur-
face of the dura, lies the pituitary body. The cavernous sinuses each receive the ophthalmie vein
anteriorly, these veins communicating with each other across the middle line by means of the inter-
cavernous sinuses, and discharging their blood posteriorly into the petrosal sinuses. The inter-
communicating veins are accordingly the homologues of the pituitary veins of my descriptions of
fishes, and the cavernous sinuses, intercavernous sinuses, and Cava Meckelii are together the appa-
rently strict homologues of the myodome of Amia; that myodome consisting, as I have already ex-
plained, of a ventral portion which is the homologue of the myodome of teleosts, and an upper lateral
chamber, on either side, which is the homologue of the trigemino-facialis chanıber of teleosts.
- The outer wall of each cavernous sinus is traversed by the oculomotorius, trochlearis and ab-
ducens nerves, by the ophthalmie and superior maxillary branches of-the trigeminus, and by the
internal carotid artery. Having traversed the wall of the sinus, the oculomotorius, trochlearis,
abducens and ophthalmieus trigemini all issue into the hind part of the orbit through the sphenoidal
fissure, that fissure lying between the great and small wings of the sphenoid bones, the former of
which is said to be formed by the alisphenoid bone and the latter by the orbitosphenoid. The fissure
is also traversed by the ophthalmiec vein as it passes from the orbit into the cavernous sinus. The
sphenoidal fissure thus corresponds in every detail, excepting in that it transmits the ophthalmieus
trigemini, to the orbital opening of the myodome of Amia. But the fissure lies, in man, between
the alisphenoid and orbitosphenoid bones, instead of between the parasphenoid and basisphenoid
legs of the alisphenoid. This however seems unimportant, for, as F have also pointed out (’97b),
the so-called basisphenoid of Amia is probably simply a part of the orbitosphenoid, ossifying from
a separate and independent center; the orbitosphenoid of Amia and Man invading a region that
is ossified as part of the alisphenoid in teleosts. Regarding the ophthalmieus trigemini, which tra-
verses the sphenoidal fissure in man, that nerve is the homologue of the ophthalmicus profundus
of fishes, a nerve not found in Amia or teleosts, but as it arises from the profundus ganglion it would
probably issue from the skull with the ciliaris profundi, which latter nerve traverses the orbital
opening of the myodome.

The foramen rotundum and the foramen ovale both perforate, in man, the great wing of the

sphenoid, and transmit respectively the superior and inferior maxillary branches of the trigeminus,
Zoologica. Heft 57. 25

— 194 —

the latter nerve being accompanied by certain meningeal vessels. The foramen rotundum is said by
Thane (Quain, vol. I, pt. I) to have been separated off from the sphenoidal fissure by the growth
of bone around the nerve, the foramen ovale being similarly cut off from the foramen lacerum. The
foramen lacerum is an aperture between the apex of the petrous portion of the temporal bone and
the body and great wing of the sphenoid, and would seem to correspond to the trigeminus foramen
ol Amia, though it may include some part also of the trigeminus opening of the trigemino-facialis
chamber of teleosts. Comparison with fishes would thus indicate that the foramen ovale and the
foramen rotundum must both be parts of the foramen lacerum, instead of being respectively parts
of that foramen and of the sphenoidal fissure. The foramen spinosum of man, which perforates the
great wing of the sphenoid and transmits the large middle meningeal vessels, must have its homologue
in one or both of those perforations of the alisphenoid that, in teleosts, transmits branches of the
external carotid artery and orbito-nasal vein.

The foramina related to the nervus facialis are not so readily homologized. The facialis foramen
and the facialis opening of the trigemino-facialis chamber of teleosts must together represent parts
of the Aqueduct of Fallopius of man, but apparently not the whole of it, for the lower part of the
aqueduct is said by Thane to be included between the outer surface of the periotie and the tympanie
plate, and until this latter plate is identified in fishes, the homologue of the stylo-mastoid foramen
can not be determined. The hiatus Fallopii, which leads from the Aqueduet of Fallopius to the
depression on the petrous that lodges the Gasserian ganglion, is evidently that part of the trigemino-
facialis chamber that lies between the facialis and trigeminus foramina; the Vidian canal being what
I have described as the palatine canal in Amia, a canal that lies between the parasphenoid (pterygoid
of man, Gaupp, ’05) and the cartilaginous basis eranii of that fish. In teleosts this canal is absent
because of the suppression of the cartilage in this region. The internal jugular vein does not, in man,
issue with the nervus facialis, issuing instead through the jugular foramen which transmits also the
glossopharyngeus, vagus and spinal accessory nerves. The internal carotid canal, which, in man,
traverses the petrous part of the temporal bone, seems not to be the exact homologue of the internal
carotid foramen of fishes, this latter foramen Iying between the proötic and parasphenoid instead of
traversing the former bone. But as the artery then traverses the cavernous sinus in man and the myo-
dome in fishes the canal of the one must be in large part the homologue of the foramen of the other.

Regarding the bones of the region, the posterior clinoid wall is represented in the mesial pro-
cesses of the proötics of Amia, the anterior clinoid wall being represented either by the basisphenoid
of teleosts, by the prepituitary part of the mesial processes of the proötics, or by those bones fused
to form a single element. The spieula of bone that, in man, sometimes unite the anterior and posterior
clinoid processes are then those parts of the mesial processes of the proötics of teleosts that lie lateral
to the pituitary opening. The parasphenoid leg of the alisphenoid of teleosts is the great wing of
the sphenoid bone of man, the basisphenoid leg of the bone of fishes apparently being suppressed
by an invading growth of the orbitosphenoid which forms the small wing of the sphenoid of man.
The basisphenoid of fishes, if it persists as a separate bone, is the presphenoid of man, but, as just
above stated, that bone of man would seem to at least include the prepituitary parts of the mesial
processes of the proötics of teleosts. The basisphenoid of man, if it is found in fishes, would seem to
be represented in a part of the proötie, but it is perhaps possible that the median ossification in the
dorsal surface of the proötie bridge of my one specimen of Gadus morrhua, described below, may
be the homologue of that bone.

— 195 —

Swinnerton, it should here be stated, has arrived, in a study of the development of Gasteros-
teus, at conclusions quite different from those just above proposed, in so far as regards the position
of the myodome relative to the cranial walls in fishes, and the homologies of the hypophysial fenestra.
According to him (°02, p. 527) those parts of the parachordals that, in embryos of Gasterosteus, bound
laterally the interparachordal fossa, become depressed in late embryonic stages, so as to appear as
mere downward processes of the proötics. These processes are said to be capped with cartilage, to
each be continued posteriorly by a ridge on the ventral surface of the posterior portion of the related
proötic, and, posterior to that bone, by a similar ridge on the ventral surface of the basioceipital.
The two processes are said to enclose between themselves the anterior portion of the myodome, which
portion is said to accordingly be an actual derivative of the cranial cavity; while the two ridges that
form posterior continuations of the processes enclose a posterior portion of the myodome, which
is said to be extracranial in position. These conclusions lead Swinnerton to the further conclusion
(l. e., p. 528) that the so-called hypophysial fenestra of the skull of adult teleosts is related to the
parachordals, alone, and hence can not be the homologue of the pituitary (hypophysial) fossa of
embryos, which fossa is related to the hind ends of the trabeculae. The so-called hypophysial fenestra
of the adult fish can not then be the homologue of the hypophysial (pituitary) fenestra of higher
animals, and Swinnerton accordingly proposes for this fenestra of the adult teleost the name inter-
parachordal fossa. The position, in the adult, of the pituitary fossa of embryos, Swinnerton does
not give; the inference being that it has wholly disappeared in that suppression of the hind ends ot
the trabeculae that is said to take place in late embryoniec stages.!)

Those teleosts in which the myodome is said to be absent can now be considered. Vrolik
(73) says that it is absent in all the Gadidae, and also in Silurus, Lophius and the eel; Gill says (’91b,
p- 363) that it is absent in the Cyclopteroidea, and also (°82) in Echeneis; Swinnerton (°02, p. 576)
says that it is absent in Fistularia and Syngnathus; and Jordan and Evermann (’98) say that the
basis cranii is simple in the Hemibranchii and Lophobranchiü, which include Fistularia and Syn-
gnathus; Cope (quoted by Gill, ’88, p. 576) says that it is absent in all the fishes of the group Seypho-
branchii, which group (Cope, ”71) includes the Uranoscopidae, Gobiidae, Blenniidae, Gobiesocidae
and Cottidae; Gierse (’04) says that it is wholly wanting in Cyelothone; and Starks (05 a) says that
it is absent in Caularchus, Callionymus and the Batrachididae, confirming also its absence in the
Gobiesocidae. MeMurrich (’84) says that it is rudimentary in Ameiurus; and Sagemehl (’91, p. 574)
says that it has undergone retrogression in Cobitis, Misgurnus, Nemachilus and Acanthophthalmus.
Boulenger (°04) says that the basis cranii is simple in the Mormyridae, Osteoglossidae, Pantodontidae,
Phractolaemidae, Stomiatidae, Gonorhynchidae, Cromeriidae, Galaxiidae, Gobiiformes, Discocephali,
Comephoriidae, Rhamphocottidae, and in all the five families of his suborder Pediculati. He further
says that the basis cranii is double in the symmetrical forms of his division I of the suborder Acantho-
pterygii; which would seem to imply that it is simple in the asymmetrical forms of the same division,
that is the Pleuronectidae. And the expression „basis cranii simple‘, while it is, strietly speaking,
descriptive of a condition of the bony skull alone, is currently considered as equivalent to -saying

!) Gaupp, in Bd. 3 of Hertwig’s Handbuch der vergleichenden und experimentellen Entwickelungslehre der Wirbel-
tiere, a work that I have only seen since this manuscript was sent to press, describes practically similar conditions in
Salmo, and arrives at practically similar conelusions regarding the homologies of the parts. This would seem to establish
the fact that the basi-oceipital portion of the myodome is extracranial in origin. Regarding the prootie portion of the
myodome, Gaupp’s descriptions would seem to confirm my contention that it is an intramural space and not an intra-
eranial one.

— 196 —

that there is no myodome. The list of fishes said, by one author or another, to be without a myodome
is thus large, and I have attempted to control it as far as my material and the literature at my disposal
will permit.

In Gadus aeglifinus, Brooks (°84) says that the proötie „unites below with its fellow of the
opposite side, and below this with the parasphenoid, the three bones bounding a deep pit, which
is open anteriorly, and gives origin to the receti muscles of the orbit“. This fish would thus seem
to possess a myodome, and as another one of the Gadidae, Gadus merlangus, is easily obtained here,
I have examined it in this connection. In this fish there is, as in G. aeglifinus, a deep pit opening
into the orbit and giving origin to certain of the recti muscles. The side walls of this pit are formed
by the ventral portions of the proöties, those portions of those bones being capped with cartilage and
not meeting in the middle line, a hypophysial fenestra, closed ventrally by the underlying para-
sphenoid, thus being left between them. The dorso-posterior wall, or roof of the pit is thick, and
is formed by the proötie bridge, that bridge being formed by the mesial processes of the proöties
united by a thick median interspace of cartilage. The cerebral surface of this roof slopes postero-
ventrally and forms a convex and triangular-shaped surface between the anterior ends of the large
saccular grooves. The wide anterior edge of the roof is bevelled, the bevelled surface sloping antero-
ventrally. The transverse edge that lies between this sloping, bevelled surface and the posterior
portion of the roof of the pit is continued dorsally, on either side, to form the anterior boundary
of the labyrinth recess. The bevelled surface gives attachment to the ventro-posterior edge of a thick
tough membrane that fills the large orbital opening of the brain case, a large pocket in this mem-
brane, immediately anterior to the proötie bridge, lodging the pituitary body. In the anterior edge
of the proötie there is, as in G. aeglifinus, a deep incisure for the exit of the trigemino-facialis nerves,
and from this incisure a groove leads ventro-mesially into the anterior end of the myodomic pit. There
is no closed foramen whatever in this part of the proötic bone, all of the nerves that pierce the bone
in Scorpaena here passing across its anterior edge. There is also no internal carotid foramen between
the proötic and parasphenoid, the internal carotid here passing inward across the anterior edge of
the expanded, postorbital portion of the parasphenoid; that edge of the parasphenoid Iying slightly
anterior to the anterior edge of the ventral portion of the proötic. The anterior end of the large
saccular groove is separated from the bottom of the trigemino-facialis incisure by only a thin layer
of bone. There is no basisphenoid, but there is, as in Cottus, a considerable basisphenoid thickening
of the membrane that closes the orbital opening of the brain case. Posterior to this thickened portion
of that membrane and partly enclosed in it, in the region of the membranous pituitary fossa, is the
transverse commissure of the pituitary veins. There is thus here a normal myodome, but it has been
shortened both anteriorly and posteriorly. Posteriorly this shortening is due to a proötie constrietion,
while anteriorly it is due to the absence of the usual enclosing bones; for it is evident that the anterior
portions of the bodies of the proöties of Scorpaena, and the entire ascending processes of the para-
sphenoid of that fish, are absent in Gadus.

In a prepared skull that I have of Gadus morrhua, the conditions are all similar to those just
described for Gadus merlangus, excepting that there is a median ossicle on the cerebral surface of
the cartilage of the proötie bridge, not found in G. merlangus. This ossicle is transverse in position
and extends from proötie to proötic along the transverse edge that is continuous, on either side, with
the anterior wall of the corresponding labyrinth recess. It is a stout ossicle, of perichondrial origin,
and has never been described in any fish so far as I can find.

le

One further condition of the Gadoid skull needs to be mentioned.‘ The hypophysial fenestra
is continued posteriorly, along the ventral surface of the interproötie cartilage, by a relatively deep
groove which is prolonged posteriorly by two short recesses in the anterior end of the basioceipital,
the two recesses being separated by a thin, vertical, median wall of bone. Laterally, on either side,
this groove is in wide communication with a large and deep recess in the proötic. This recess extends
antero-dorsally in the bone, Iying immediately mesial to the saccular groove and tapering toward
its dorso-anterior end, which end lies slightly postero-mesial to the trigemino-facialis ineisure. The
bone that forms the outer wall of the recess is thin, and seems to be of purely perichondrial origin.
In the specimens of Gadus merlangus that were particularly examined in this connection, and which
were all fresh specimens that had been slightly boiled, this recess was filled with loose and apparently
fatty tissue: but in the skull that I have of Gadus morrhua, which had not been boiled, the recess
lodged the spreading lateral portions of a membrane that covered the ventral surfaces of the proöties
and the interproötie cartilage, Iying between those structures and the underlying parasphenoid. The
recess is certainly the homologue of the proötie vacuity found in the proötic of the 45 mm Scorpaena,
as stated when describing that fish.

In Uranoscopus scaber the interorbital wall is thick, and is deeply and widely excavated, on
its dorso-anterior edge, by the large rostral depression. The central portion of the floor of this
depression is formed by the subeircular mesethmoid, the ventral surface of which bone rests directly
upon the underlying parasphenoid and, perhaps, also on the vomer; but the existence of this latter
contact was not established. The anterior portions of the side walls of the depression are formed
by the deeply excavated ectethmoids, the posterior halves of the same walls, and the hind wall,
being formed by a specially developed flange of the frontal of either side. No alisphenoid is evident
as a separate bone, but it would seem to be represented in, or at least to be replaced by, what appears
as an anterior process of the sphenotic. With a ventral process of this alisphenoid part of the
sphenotic, and also with an adjoining portion of the anterior edge of the proötic, the ascending process
of the parasphenoid is in contact. Posterior to this ventral process, the truncus maxillo-mandibularis
trigemini, undoubtedly accompanied by the buccalis lateralis, issues through a perforation of the
side wall of a well-developed trigemino-facialis chamber. The ramus ophthalmicus superficialis
issues from the same chamber through a foramen that lies between the suturating edges of the
parasphenoid and the ventral process of the alisphenoid portion of the sphenotic. This ventral process
is, accordingly, a well developed parasphenoid leg of the alisphenoid process of the sphenotic.

Between the parasphenoid leg of the alisphenoid process and the body of that process, dorsally,
the parasphenoid posteriorly and ventrally, and the rostral flange of the frontal and the cartilage
covering the ventral part of that flange, anteriorly, there is a large subeircular opening. This opening
gives exit to the olfactorius, opticus, oculomotorius and trochlearis nerves, and gives entrance to
certain of the muscles of the eye, how many or which of them was not determined. The opening
is accordingly, in function, an olfactorio-optieus fenestra and an orbital opening of the myodome
combined. On the internal surface of the proötie, at a certain distance posterior to the hind edge
of this opening, there is a low transverse and nearly vertical flange which suturates in the middle
line with its fellow of the opposite side. That part of the eranial cavity of the prepared skull that
lies anterior to this transverse vertical flange forms a recess in the cranial floor, but belongs properly
to the orbit and not to the cranial cavity. The canal for the internal carotid passes inward between
the proötic and the hind edge of the ascending process of the parasphenoid, and opens on the floor

— 198 —

of the recess. The membranes closing this recess toward the eranial cavity were not investigated,
but the recess is certainly a myodomie recess, similar to, and as well developed as, that recess in
Gadus. Uranoscopus thus has a myodome of the kind found in Gadus. It furthermore has a proötie
vacuity larger even than the vacuity in Gadus, and which, as in Gadus, extends posteriorly into
the anterior end of the basioceipital.

In Blennius gattorugine the posterior portion of the ventral edge of the proötie is thick and
grooved, the mesial edge of this groove representing the mesial process of the bone, and the other
edge representing the ventral portion of the body of the bone. Anterior to the groove the actual
ventral edge of the bone is formed by the mesial edge of its mesial process. This edge of the bone,
as also both edges of the posterior, grooved portion, are widely separated from the corresponding
portions of the bone of the opposite side, the space between the mesial processes being bridged by
a membrane which underlies the hypoaria and pituitary body. Anteriorly, this membrane is attached
to the hind edge of the basisphenoid, that bone being, in this fish, unusually wide in an antero-posterior
direction. Beneath this membrane and the basisphenoid, between them and the underlying para-
sphenoid, there is a long and relatively large space which lodges certain of the eye muscles and is
accordingly a well developed and perfeetly normal myodome. The pituitary opening and the hypo-
physial fenestra are simply unusually large, and the pituitary opening lies much further posteriorly
than in Scomber and Scorpaena.

In Lophius piscatorius there is, in the prepared skull, no myodome, as Vrolik has stated.
In the fresh skull, however, there is a pocket between the bony floor of the skull and an overlying
membrane, and in this pocket certain of the eye-muscles have their origin. The pocket is accordingly
a myodome. The overlying membrane is thick and strong, and forms the hind wall of the orbit as
well as the roof of the myodome. Laterally, on either side, it extends upward and forms, as in Amia,
the mesial wall of the trigemino-facialis chamber. The membrane is thus similar to that in Amia,
but it is even more extensive than in that fish, for it entirely replaces, in Lophius, the bony mesial
processes of the proötices.

In both Syngnathus and Hippocampus, which I have examined in serial sections, there is a large
myodome, roofed, in Syngnathus, entirely by membrane, while in Hippocampus the recti externi extend
backward beyond the other muscles and pass beneath the cranial floor, between it and the parasphenoid.

In Gymnarchus, of the Mormyridae, a dilapidated skull of which I have, there is apparently
no myodome, the conditions here being similar to those found in Ameiurus, which will be later de-
scribed; but in two other members of the family, Mormyrops deliciosus and Petrocephalus bane,
Ridewood (’04b) says there is a myodome.

In Osteoglossum Leichardti and Heterotis niloticus, of the Osteoglossidae, Ridewood (’05a)
says there is a myodome; as there also is, according to the same author, in Pantodon Buchholzi and
Phractolaemus Ansorgi.

In Galaxias of the Galaxiidae, Swinnerton (’03) says there is a myodome.

In Pleuronectes platessa, Cole & Johnston (’01, p. 13) say there is a myodome.

In Echeneis, of Boulanger’s Discocephali, I find, ventro-antero-mesial to the trigemino-facialis
chamber, a large aperture, which, in the prepared skull, leads directly into the cranial cavity, along
its floor. The aperture is bounded dorso-mesially by a bone that must be the basisphenoid, although
the sutures in this region can not be distinguished in my one specimen; and from the hind edge of
this bone a strong membrane extends, in the recent state, backward and downward and is attached

— 199 —

to the floor of the cranial cavity. Through the aperture and into the space roofed by this membrane,
certain of the eye muscles extend, the space thus being a perfectly normal myodome.

Of the Cottidae, said by Cope to be without a myodome, I have described it in the present
work, well developed, in Cottus octodecimospinosus; and Gill (’91b) gives as one of the characteristics
of his family Cottoidea, ‚„Myodome more or less developed“.

Of the Rhamphocottidae, I have no specimens, but the Cottidae having a myodome, certainly
well developed in some species, it must surely be also found in the closely related Rhamphocottidae.

In Gonorhynchus greyi, Ridewood (’05b) says there is a myodome.

Of the entire list of fishes said to be without a myodome, all of the individual species mentioned,
excepting only Caularchus, Callionymus, Fistularia, Cyclothone, Silurus and the eel, are thus shown
to have that canal; while of the several families in which the canal is said to be absent, some one or
more members of each family, or of a closely related subfamily, are also shown to have it, excepting
only the Cyelopteroidea, Cromeriidae, Gobiidae, Gobiesocidae, Stomiatidae, Batrachididae and
Comephoridae. Of the Cyelopteroidea, Cromeriidae, Gobiesocidae, Stomiatidae, Batrachididae and
Comephoridae, I have no specimens; neither have I of Caularchus, Callionymus, Fistularia or Cyclo-
thone. These fishes must accordingly be left out of consideration. Of Fistularia, it may, however,
be stated that Swinnerton shows a myodome in Gasterosteus, and that I find a well-developed myodome
in Centriscus, both of which fishes belong with Fistularia to the Hemibranchiil. Of the Siluridae,
Muraenidae, and Gobiidae, I have specimens and they can now be considered.

In Conger conger of the Muraenidae, there is, at the hind end of the orbit, a small median
transverse shelf of bone which projects forward slightly above the parasphenoid. The optie nerves
leave the cranial cavity along the dorsal surface of this shelf, and beneath it, between it and
the parasphenoid, the recti muscles have their origins. The bones of the skull are here all so
firmly ankylosed in my specimens that I can not with certainty identify them, but the shelf of bone
must certainly be either a basisphenoid, a proötic bridge similar to the bridge of Gadus, or a trans-
verse ridge of the parasphenoid, as in Dactylopterus. And in either case the little space between
the bone and the body of the parasphenoid would be a perfectly normal but very much reduced
myodome. Ina series of sections that I have of a young Conger, the recti muscles all seem to
arıse from a delicate median membrane, which lies partly beneath and partly anterior to the shelt
of bone, each muscle arising directly opposite its fellow of the opposite side; no one of the muscles,
apparently, having its origin either on the shelf or on the parasphenoid bone.

In a single small specimen of Gobius eruentatus that I have been able to obtain, the arrange-
ment seems to be exactly similar to that in Dactylopterus. The proötie has a narrow orbital surface
which lies at a slight angle to that part of the bone that lies immediately posterior to it and that
forms the uniformly thin floor of this part of the cranial cavity. The narrow orbital surfaces of the
bones of opposite sides are separated by a wide median interval, and the ventral part of this interval
is filled by a transverse ridge on the dorsal surface of the parasphenoid. This ridge on the para-
sphenoid has the same antero-dorsal inclination as the orbital surfaces of the proöties, and forms
the hind wall of a small pocket which lies at the hind end of the orbits, and recalls both the myodomie
pocket of Gadus, and the myodome of Dactylopterus.

Of Silurus I can find no description that is of value in this connection. But MeMurrich’s
('84) descriptions of Ameiurus catus (nebulosus) are of value, and, as I have a few specimens of this
fish, it can be described. Short reference must, however, first be made to Sagemehl’s descriptions of

— 200 —

the Cyprinidae. According to that author (°91, p. 574), a well developed myodome is found in most
of these fishes. In Cobitis, Misgurnus, Nemachilus and Acanthophthalmus, all of which have small
eyes, the myodome is said to have undergone retrogression. The weak muscles of the eye are said to
all arise in the postero-ventral corner of the orbit, none of them entering the cranial cavity. The
anterior edge of the proötic is said to be formed of two lamellae one lying above the other, the dorsal
one ending with a free anterior edge, while the ventral one forms the floor of the cranial cavity.
The slit-like space between the two lamellae, although it lies considerably posterior to the hind end _
of the orbit, is said to unquestionably represent a myodome that has undergone reduction. Reference
to the figures of Cobitis fossilis (pl. 29, fig. 12) shows that the dorsal lamella must be a rudimentary
mesial process of the proötic, and as such Sagemehl doubtless considered it, although he does not
definitely describe it as such. Anterior to this process, there is said (l. c., p. 549) to be a wide rhom-
boidal hypophysial fenestra. The nervus abducens, in those Cyprinidae that are said to have no
myodome, and of which Cobitis is one, is said not to perforate the mesial process of the proötic, but
to apparently issue by the large optie fenestra. The condition of the myodome is thus here closely
similar to that in Lepidosteus; that posterior portion of the canal that I have referred to as the
saceular space, existing in a reduced condition, well within the brain case, widely separated from
the orbit, and in no direct relation whatever to any of the eye-muscles. This condition is thus the
reverse of that found in Dactylopterus, Gobius and Gadus, in which fishes this part of the myodome
has been crowded out of the cranıal cavity into the orbit.

Ameiurus can now be considered, and of this fish I have one skull, prepared some years ago
and partly disarticulated, and a few small alcoholic specimens. Of Ameiurus, Me Murrich says:
„Below the proöties, where they meet in the middle line below, and between them and the anterior
portion of the basioceipital above, and the parasphenoid below, is a small cavity. This is the almost
aborted rudiment of the canal for the orbital muscles, which is largely developed in many fishes,
but absent or rudimentary in Silurus, Ameiurus, Gadus, Lophius etc.“

This description of the conditions in Ameiurus is not very satisfactory, and it is not explained,
either here or elsewhere in the descriptions, that this so-called rudimentary myodome is widely
separated from the orbit and out of all relation to the eye-muscles. Yet such is the case. In the
anterior three-fifths, approximately, of its length, the ventral edge of the proötic does not meet its
fellow of the opposite side, a wide hypophysial fenestra, closed ventrally by the parasphenoid, being
left between the two bones. Posterior to this fenestra, the ventral edges of the proötics meet in the
middle line, and the two bones there form, on the floor of the cranial cavity, a prominent transverse
bolster which has closely the position of the cross-canal of Lepidosteus; and it is certainly in this
bolster that MeMurrich found the small cavity that he considered as a rudimentary myodome. In
two of my small specimens there was no indication whatever of such a cavity; the bolster there being
completely filled with cartilage, but having, on its anterior surface, a slight median depression which
doubtless lodged the saccus vasculosus. In one other specimen, there was a median cavity extending
under, rather than into the bolster, while in a fourth specimen there was a smaller but similar cavity
on one side only of the median line. The pituitary body lies immediately anterior to the bolster,
directly above the hypophysial fenestra, and a vein that apparently drains the pituitary region
begins here and runs directly forward along the floor of the cranial cavity, soon separating into two
parts, one on either side. The venous cross-comissure of Lepidosteus thus here seems replaced by
a median vein, this being a variation in detail but not in prineiple. The eye-muscles all have their

— 201 —

origins ventral to and between the optice and trigemino-facialis foramina, on the outer surface of
that median process of the parasphenoid that MeMurrich considers as a basisphenoid completely
ankylosed with the parasphenoid, but which Sagemehl (°91, p. 575) considers, in Silurus, as a simple
process of the parasphenoid; none of the muscles entering the eranial cavity. It may furthermore
here be stated that these muscles are said by Workman (°00) to be innervated as they are in Amia,
and hence as I have shown them to also be in Lepidosteus (present work), and that Ameiurus is the
only teleost in which this manner of innervation has, as yet, been described.

Ameiurus thus presents conditions similar to but even more extreme than those in Lepidosteus,
the cross-canal of the latter fish here being a solid bolster, due, quite undoubtedly, to the invading
growth of the surrounding cartilage. Yet, the condition in Ameiurus is said (McMurrich) to represent
an aborted condition of the teleostean myodome, while that in Lepidosteus is said (Sagemehl) to
represent a condition from which that myodome was developed! Wishing to determine which of these
two directly opposed assumptions is the correct one, I have consulted the geological record, and,
while that record certainly does not give a definite solution, it has suggested what seems to me such
a solution; for it has led me to ascribe a totally different motive to the origin of the myodome than
that proposed by Sagemehl, which, as is well known, is the simple seeking of a better point of origin
by one or more of the muscles of the eyeball.

Aceording to Zittel (’87— 90), whom I have selected because of the convenient tables given,
representatives of the families Siluridae and Ginglymodi, in the latter of which the living Lepidostei
are placed, are found in the Eocene formations, and no earlier; and in all the living representatives
of these two families that have been examined in this connection, there is no functional myodome.
Representatives of the family Halecomorphi, in which Amia, with a well developed mıyodome, is
placed, are found considerably earlier, in the Jurassic deposits. Certain other families of the Lepi-
dosteidae occur earlier than any of the Amiadae, the Stylodontidae being found in the Dyas (Permian)
deposits; but, as two Jurassie representatives of this latter family, Lepidotus and Dapedius, are
said by Woodward (°93) to have a „basicranial canal‘“ — that is a myodome — it is evident that
Lepidosteus can not descend from them, if its myodome represents a primary condition.

The earliest teleosts are said by Zittel to be the Hoplopleuridae and Clupeidae, both of which
are said to be found in the Triassie, considerably earlier than the families Siluridae and Ginglymodi,
and as early, even, as any representatives of the order Lepidosteidae excepting only the Stylodontidae.
Of these two families of teleosts the Hoplopleuridae are extinet, while the Clupeidae are well represented
by living species, several of which, Clupea, Elops, Albula and Megalops, are known to have a well-
developed myodome. . In Clupea harengus. which I have examined for this purpose, the proötie bridge
is thick and has a bevelled anterior edge which slopes antero-ventrally, the whole bridge much
resembling that of Gadus excepting that it lies in a horizontal instead of a strongly inclined position.

Several other families of teleosts existed at the beginning of the Cretaceous period, and hence
earlier than the Ginglymodi and Siluridae. These families are the Saurocephalidae (extinct), Strato-
dontidae (extinet), Salmonidae and Seopelidae, all placed by Zittel in his order Physostoni; the
Labridae and Chromidae of his order Pharyngognathi; and the Berycidae, Sparidae, Xiphiidae,
Carangidae, Cataphracti, Gobiidae and Aulostomi of his order Acanthopteri. In living represent-
atives of these several families, Parker shows a myodome in Salmo salar, of the Salmonidae; in
Dactylopterus and Peristedion, of the living Cataphracti, I have described it in the present work:

in Gobius of the Gobiidae, a myodome similar to that in Dactylopterus is found, as also already
Zoologica. Heft 57. 26

described in the present work: in Scopelus of the Scopelidae, Supino ('01/02) shows a large myodome,
and I find one in Saurus griseus of the same family: in Crenilabrus pavo, of the Labridae, and in
Trachurus trachurus, of the Carangidae, I find a myodome well and normally developed: in Hoplo-
stethus, of the Berycidae, Supino (°04) shows a normal myodome, and Starks (°04, p. 602) gives, as
one of the characteristics of the Berycoidea, „Myodome large in front, closed abruptly behind, or
open to the exterior posteriorly only through a pore‘‘: in Fistularia, of the Aulostomi, it is said by
Swinnerton not to be developed, but, as already stated, this may be incorrect: in a Mediterranean
Sargus, and in Chrysophrys aurata, both of the Sparidae, I find a well developed myodome; as I also
do in a Mediterranean Xiphias of the Xiphiidae.

It is thus seen that a myodome is found in certain living representatives of nearly all of the
earliest known families of teleosts; and that certain of these families, certain of the living represent-
atives of which possess a myodome, are found in earlier geological periods than any of the families
of the Teleostei the living representatives of which are known not to possess it. Certain of the Stylo-
dontidae, the earliest known representatives of the Lepidosteidae, are also said to possess a myodome.
The palaeontological record, as given by Zittel, thus certainly indicates that the conditions from
which the myodome is developed are not to be looked for in either Lepidosteus or Silurus, but in
fishes belonging to earlier deposits than those in which those teleosts and ganoids that possess a myo-
dome are found; and the only fishes so found, living representatives of which are known, are, in
Zittel’s terminology, the Selachii, Dipnoi, Chondrostei, and Crossopterygi.

In the Selachii, Gegenbaur (’72) shows a thick interorbital wall, and a pituitary fossa (Sattel-
grube) which lies between, or but little posterior to, the posterior portions of the orbits. The canalıs
transversus, which transmits the pituitary vein, lies in or beneath the bottom of this fossa (Hexanchus,
Mustelus, Galeus), or but slightly posterior to it (Heptanchus, Sceymnus). In Ceratodus (Bing & Burck-
hardt, 05, P. 523) a similar interorbital wall and pituitary fossa are found; and the same is true of
Acipenser (Parker, ’82a). In Polypterus there is a thick interorbital wall, and Pollard (92) shows,
in the cranial cavity of this fish, a cartilaginous shelf which, as already stated, closely resembles the
proötic bridge of Amia. Bing & Burckhardt (’05, p. 571) show this bridge much more inclined than
Pollard shows it, and they show, as Pollard does, what is probably the sacceus vasculosus, projecting
backward beneath the bridge. No mention is made, in either Ceratodus, Acipenser or Polypterus,
of a canalis transversus or pituitary vein, but this vein must certainly exist in each of these fishes,
and must lead into the orbit of either side, as it does in the Selachii and Teleostei. Imagine the orbits,
in either one of these several fishes, to be enlarged and deepened. This would necessarily shorten
the canal traversed by the pituitary vein, and would, if sufficiently continued, bring the pituitary
fossa into the hind ends of the orbits, much as it is actually found in Dactylopterus and Gadus. Üertain
of the eye-muscles would then almost necessarily have their points of origin transferred to this pituitary
pocket, and a myodome would be established.

This being accepted as the manner of origin of the myodome, do Lepidosteus and the Siluridae
present a primary or a secondary condition? It is evident that they might be considered as presenting
either one or the other, but it seems to me that both of them present a primary condition, for, as
already stated, if the anterior edge of the proötie bridge of Polypterus were to be bent downward
until it touched and coalesced, everywhere excepting in the middle line, with the underlying floor
of the cranial cavity, it would give rise to a condition closely resembling that found in Lepidosteus;
and if the cross-canal, thus produced, were to be invaded by the surrounding cartilage until only

0

a slight pit was left on its anterior surface, it would give rise to the conditions found in Ameiurus.
Under this assumption the condition of the myodomic region, as it exists, both in Lepidosteus and
Ameiurus, would be primary and not derived secondarily from a pre-existing myodome. But this
presupposes, if Ameiurus can be considered as typical of the Siluridae, either that the Weberian
apparatus has been developed independently in the Siluridae and the other families of the Ostario-
physi, or that the myodome has been developed, in those families of the Ostariophysi in which it is
found, wholly independently of its development in other teleosts. For that a myodome could have
been developed from the condition found in Ameiurus seems most improbable, Ameiurus quite cer-
tainly representing the end of a line in which the saccular portion of the nıyodomie region is aborting,
whether it be primarily or secondarily.

Still another suggestion regarding the myodome is that its basioceipital extension may have
been developed in relation to a vertebral depression on the anterior surface of that bone. In Trigla
lyra, I have shown that, that depression in the anterior end ofthe basioceipital that lodges the posterior
portion of the myodome is lined with a layer of dense bone that is similar to the bone that lines
the vertebral depression in the hind end of the same bone, and that these two linings of dense bone
are connected by a small median line of similar bone. This suggests, as I have already stated, that
the myodomie depression on the anterior end of the basioceipital of this fish is, like the depression
on its hind end, a vertebral depression, and if this be true of this fish, it must also be true of all other
fishes in which the myodome has a basioccipital extension. In Gadus and Saurus the myodome
has no basioceipital extension, but in both these fishes there is, nevertheless, a depression on the
anterior end of the basioceipital, and this depression — although lodging no part of the myodome —
would certainly seem to be the homologue of the myodomic depression of other fishes. This depression,
in Gadus and Saurus, is continuous with a large vacuity in the hind edge of the prootie, and if the
one is a vertebral depression on the anterior end of the basioccipital the suggestion is evident that
the other might bea depression in some way related toa similar depression on the hind end of the proötie.
The proötic vacuity both of Gadus and of Saurus is in communication, by the intermediation of the
hypophysial fenestra, with the myodomie pocket on the anterior surface of the proötic. The sup-
position is thus evident that a myodomic pocket might have been first developed in relation to a
vertebral depression on the anterior surface of the proötic region, and that this depression, pushing
backward and gradually obliterating or absorbing a similar depression on the posterior surface of the
same region, and then even occupying also a vertebral depression on theanterior end of the basioccip-
ital, has given rise to all known forms of the myodome. But this necessarily attributes a vertebral
origin to the basioccipital and proötic, for which, in the case of the proötic, there is no apparent
warrant. Furthermore, according to Swimnerton’s descriptions of the development of the basioeccipital
in Gasterosteus, even the depression in the anterior end of that bone can not be a vertebral one. For
that author says (02, p. 524) that, in that fish, a erest of membrane bone grows downward, in the
middle line, from the ventral surface of the primary portion of the basioceipital, and that „within
the substance of the fore part of this crest is a cavity which opens in front and receives the hinder
end of the external rectus muscle; this is the homologue of the anterior conical excavation of the
basioccipital of the Pike and many other teleosts“.

Summary.

1. The mesethmoid processes of fishes are processes of the mesethmoid bone, or of the
ethmoid cartilage, that give origin to the ethmo-maxillary ligament, and that support or give
attachment to the hind end of the nasal of either side. In the Loricati they are prominent processes
of the mesethmoid; in Trigla and Peristedion they are small processes of the same bone, wholly
concealed beneath the nasals; while in Dactylopterus they are small processes of the ethmoid
cartilage.

2. The dilatator, temporal and supratemporal fossae of fishes are grooves on the dorsal surface
of the primary cranium, more or less completely roofed by dermal bones. Each of these grooves may
have an anterior extension that lies upon the outer surface of the dermal bones of the roof of the skull,
as in Scomber. In the mail-cheeked fishes, these anterior extensions are not found, but the areas
occupied by them in Scomber are represented, on either side of the dorsal surface of the skull of the
Loricati, by contiguous regions bounded by four more or less developed ridges that radiate approx-
imately from the frontal spine. The ridge between the anterior extensions of the temporal and
supratemporal fossae is in a measure continuous with the epiotie ridge on the posterior surface of
the skull, and the posterior semieircular canal lies internal to this latter ridge. The ridge between
the anterior extensions of the temporal and dilatator fossae is similarly continuous with the ridge
that forms the boundary between the posterior and lateral surfaces of the skull, and the posterior
leg of the external semieircular canal lies internal to a portion of this ridge. The ridge forming
the anterior boundary of the anterior extension of the dilatator fossa is approximately continuous
with the ridge that separates the hind wall of the orbit from the lateral surface of the brain case,
and the summit of the anterior semicircular canal lies in a measure internal to it. The position
of the frontal spine, from which these several ridges radiate, corresponds somewhat to that of the
opening of the endolymphatie tube in selachians. The subtemporal fossa, on the lateral surface
of the skull, lies between the external semieireular canal and the utriculus.

The temporal fossa may have an epiotic diverticulum, and it may also have, as in Amia, an
anterior diverticulum. This latter diverticulum lies on the dorsal surface of the primary cranıum,
beneath the dermal bones of the roof of the skull, and in certain fishes (Elops, Albula) it becomes a
large and important portion of the fossa. But this anterior diverticulum of the fossa is not to be
confounded with the anterior extension just above referred to, the former lying ventral and the latter
dorsal to the dermal bones.

The anterior extensions of the supratemporal grooves have coalesced in the Loricati to form
the subquadrangular groove on the vertex.

3. The premaxillary of the mail-cheeked fishes has, on its anterior end, two processes, one of
which is the ascending process properly so-called, and the other an articular process; but the two
processes together are usually referred to as the ascending process of the bone.

The articular process is probably the earlier acquisition of the two, is apparently found in
all osseous fishes, and it, alone, is sometimes miscalled the ascending process of the bone (Amia,
Salmo).

The ascending process is formed by the fusion with the premaxillary of a supraethmoid bone,
the latter bone being primarily developed in protective relation to a line of latero-sensory organs,
and being so found, not only in certain ganoids (Amia, Polypterus) but also in Elops and probably

— 205 —

in Belone, these two teleosts being the only ones in which it is known to occur. In Belone the bone
is indistinguishably fused with the premaxillary, while in Elops it is found as an independent ossicle.

4. The maxillary of the mail-cheeked fishes has, on its anterior end, a process thatmay be called
its ascending process. This process gives articulation to the artieular process of the premaxillary,
and itself artieulates, by the intermediation of a pad of semi-cartilaginous tissue, with the dorsal
surface of the ascending process of the vomer. This process of the maxillary is apparently found
in all the Acanthopterygii and Anacanthini of Günther’s classification, but it is not evident in all
descriptions of the Physostomi. In those fishes in which it is found it varies greatly in its development,
and may even be found as two instead of as a single process.

5. The vomer of fishes is primarily a bone, doubtless paired, that is developed in relation
to tooth-bearing plates on the dorsal surface of the mouth cavity; and it was primarily limited to
the roof of that cavity. In certain teleosts, however, this tooth-bearing plate has acquired a dorsal
limb which may be said to consist of a head and two ascending processes, one on either side; and
these ascending processes are quite certainly formed by the fusion, with the tooth-bearing plate,
of the pre-ethmoid (septomaxillary, Amia) bone of either side. When the pre-ethmoids are found
as independent ossifications the vomer is without ascending processes. The ascending process of
either side gives articulation to the ascending process of the corresponding maxillary.

6. The septomaxillary of the Amphibia and the higher vertebrates is probably represented
in fishes by the antorbital bone of Amia, that bone being developed in protective relation to the
infranasal portion of the latero-sensory canals. This antorbital, latero-sensory bone is found in
Polypterus and Elops, as well as in Amia, and is possibly also found in certain of the Siluridae (Pollard).
In Polypterus it fuses with the premaxillary to form an infranasal process of that bone.

7. In Macrodon there is a bone, called by Sagemehl the accessory palatine, that is apparently
developed in the maxillary breathing valve of the fish, and that is accordingly the homologue of the
so-called vomer of Polypterus. It has never been recognised in any other teleost.

8. The palato-quadrate articulations with the ethmoid region of the skull differ considerably
in different ones of the mail-cheeked fishes examined. In Scorpaena and Sebastes there are two of
these articulations, one with an anterior palatine process of the ethmoid cartilage and the other with
the ectethmoid; the lachrymal also articulating with the latter bone. In Cottus the articulation
with.the ectethmoid is suppressed, the palatine there being bound to the lachrymal and that bone
alone articulating with the ectethmoid. In Trigla, this posterior articulation, with the ectethmoid,
is much as in Cottus, while the anterior articulation, with the ethmoid cartilage, has been largely
replaced by a swinging articulation (or attachment) of the lachrymal and palatine with the antero-
lateral corner of the nasal bone. In Dactylopterus this latter articulation is still more pronounced.

9. The quadrate has, in most if not in all teleosts, a posterior process which forms the posterior
boundary of the symplectie groove on the internal surface of the bone and has supporting relations
with the preopercular. This process of the quadrate is not found, as a part of that bone, in the bony
ganoids, but it is elsewhere represented both in Amia and Lepidosteus. In Amia it has fused with
the symplectic to form a process of that bone that gives a supplementary articulation to the mandible;
while in Lepidosteus it is the independent, so-called preoperculum of Parker’s descriptions (interoper-
culum, Collinge), which, in that fish, has an independent articulation with the quadrate. In the
Muraenidae, the process and the sympleetic seem to both be indistinguishably fused with the body
of the quadrate.

206 —

The so-called quadrates of osseous fishes are thus not all equivalent structures. The articula-
tions of the mandible with the suspensorial apparatus are also not all similar; Amia being the one
known exception to the otherwise general rule, but Lepidosteus somewhat resembling it. A further
development of the conditions found in Amia might transfer the mandibular articulation from the
palato-quadrate to the hyomandibular.

10. On the hind edge of the metapterygoid, in all of the mail-cheeked fishes examined ex-
cepting Cottus and Dactylopterus, there are two flanges, apparently of membrane (exosteal) origin,
one of which is lateral and the other mesial in position. Between these two flanges the external
carotid artery runs downward to fall into the arteria hyoidea shortly before that artery joins the
opereular hemibranch, and after ıt has passed from the external to the internal surface of the
palato-quadrate apparatus. On the opposing surfaces of the two flanges the lavator arcus palatini
muscle has the larger part of its surface of insertion.

In Cottus and Dactylopterus these two flanges, instead of being one lateral and the other
mesial, are respectively one ventral and the other dorsal; both flanges Iying in the plane of the
body of the metapterygoid, with their adjoining edges fused but perforated by a foramen which
transmits the external carotid and represents the V-shaped space between the flanges in the other
fishes. In these two fishes the flanges appear to be of endosteal rather than of exosteal origin.

In Amia the lateral one of these two flanges is represented in the so-called metapterygoid
process of the metapterygoid, the mesial flange being represented in that part of the body of the
metapterygoid that lies posterior to the process. In Amia both these parts of the bone are quite
evidently of endosteal origin.

11. In all of the mail-cheeked fishes examined there is a vessel, apparently an artery, that
arises in connection with what seem to be either glomuses or rudimentary glandular structures
related to the efferent arteries of the first three branchial arches. Certain evident connections of
these glomuses with the Iymphatic vessels were found, and occasional apparent connections with
the arteries, but no indication whatever of a connection with the venous system. The vessel
parallels the common carotid and its branches, and peripherally the walls of the branches of the
vessel change abruptly in character, and there appear as Iymphatic spaces. The fact that the
external carotid branch of the vessel traverses the trigemino-facialis chamber in much the position
of the hyo-opereularis artery of Amia, led me at first to homologize the vessel with that artery,
but as there is much doubt of the correctness of this homologization 1 have described the vessel as
the vesselx. In Dactylopterus one branch of the vessel seemed to enter the opercular hemibranch. In
Polyodon the system is much more developed than in the mail-cheeked fishes, and I am investigating
it in that fish. It would seem as if the glomuses from which the vessel arises might be serial
homologues of certain of the nephritie structures, and possibly also homologues of the so-called
thymus of Polypterus.

12. The external carotid, in all the fishes examined, traverses the trigemino-facialis chamber,
gives off several branches, and then terminates in a branch which turns downward between two
flanges on the hind edge of the metapterygoid and falls into the arteria hyoidea shortly before that
artery enters the opercular hemibranch. This terminal portion of the external carotid corresponds
closely in position to, and is probably the homologue of the secondary afferent pseudobranchial artery
of my descriptions of Amia, and its connection with the arteria hyoidea, instead of with the
pseudobranch, would give origin to the teleostean arrangement.

207 —

13. The alisphenoid is perforated, in Scorpaena, Trigla and Lepidotrigla, by a foramen which
transmits delicate branches of the external carotid artery and the vessel x, these branches being
accompanied by a nerve which is composed of the lateralis fibers destined to innervate the terminal
organ of the supraorbital canal and of certain other general cutaneous or communis fibers. In Dactylo-
pterus, the nerve that traverses tke foramen does not contain lateralis fibers; the nerve destined to
supply the terminal organ of the supraorbital canal there having an extracranial course. The ali-
sphenoid is also perforated, or notched, in Scorpaena, Trigla and Lepidotrigla by another foramen,
which transmits the homologue of the anterior cerebral vein of my descriptions of Amia. These
foramina, one or both, are found in the other mail-cheeked fishes also, but the arteries and veins
that traverse them were not there traced.

14. The parietal is iused, in all the mail-cheeked fishes examined, with a mesial extra-
scapular latero-sensory element to form a single bone, which I have called the parieto-extra-
scapular. This same fusion of these two bones is also found in the Characinidae and Cyprinidae
(Allıs ’04) and has been definitely established in no other fishes that I know of, excepting Chanos.

15. The side walls and floor of the skull of osseous fishes are more or less completely double
in the sphenoid (orbito-temporal, Gaupp) and labyrinth regions; these walls being there represented
in varying proportions by membrane, cartilage or bone. Between the two walls, in the sphenoid
region, lies the myodome with its upper lateral or trigemino-facialis chambers, while between the two
walls in the labyrinth region lie the membranous ears. The myodome and its trigemino-facialis
chambers are thus all intramural spaces. The floor of the myodome proper is perforated by the
hypophysial fenestra, while its roof is perforated by the pituitary opening. These two perforations
of the cranial floor are doubtless strietly homologous in all vertebrates, but it must be determined,
in each case, which one of the two perforations is in question. The myodome proper lodges a cross-
commissure of the pituitary veins, and is the probable homologue of the cavernous and intercavernous
sinuses of the human skull. The postpituitary portion of its roof apparently always chondrifies,
and is the postelinoid wall. The prepituitary portion of its roof does not usually chondrify (Argyro-
pelecus may be an exception), and it and the basisphenoid, one or both, represent the anterior clinoid
wall. The orbital opening of the myodome, on either side, is the sphenoidal fissure.

The trigemino-facialis chamber of either side is, in the mail-cheeked fishes, and probably
in most other teleosts, separated from the myodome by a partition of bone. It lodges the trigeminus
and related sympathetie ganglia, and is the homologue of the cavum Meckelii of the human skull.
Its outer wall is, in all the mail-cheeked fishes examined, excepting Cottus, represented by a narrow
bridge of bone, this wall of the chamber here forming the outer surface of the skull. In Cottus this
outer wall is entirely of membrane, the inner wall of the chamber thus here forming the outer surface
of the prepared skull. The internal wall of the chamber forms part of the bounding walls of a recess
on the internal surface of the skull, and this recess lodges the lateralis and communis portions of the
V— VII ganglionie complex. In Amia these portions of the ganglionice complex lie in the upper lateral
chamber of the myodome. There is accordingly question as to whether the inner wall of the chamber
of teleosts corresponds exactly to the same wall in Amia. In any event, the recess that lodges, in
teleosts, the lateralis and communis ganglia would seem to be the homologue of some part of the
aqueduct of Fallopius.

The trigemino-facialis chamber is continued anteriorly by an intramural space that lodges the
jugular vein and the truncus ciliaris profundi. The outer wall of this space is largely of membrane in

— 208 —

all the mail-cheeked fishes examined, excepting Cottus, and there appears as a jugular groove on the
outer surface of the prepared skull. In Cottus the outer wall of the space is of bone and the inner
wall largely of membrane, the space there appearing as a recess on the inner surface of the prepared
skull. The outer wall of the space, primarily of, membrane, is invaded to a different extent, in different
fiıshes, by the neighbouring bones, thus giving rise to greatly varying conditions.

16. The myodome of fishes is primarily a subpituitary space that is connected with the
orbit of either side, or with the orbital region, by a canal that transmits the pituitary vein.
Secondarily this subpituitary space acquires a wide communication with the orbits, the primal
cause of this secondarily acquired communication apparently being a deepening of the hind ends
of the orbits due to a marked enlargement of the eyeballs. Following this deepening of the
orbits, certain of the eye-muscles of either side enter the pituitary canal and, enlarging that
canal, finally wholly break down the wall that separates the orbits from the subpituitary space.

It seems possible that the subpituitary space may represent the conical depression on the
anterior surface of the body of a vertebra, the later acquired, posterior, or basioccipital extension
of the myodome then possibly being due to the assimilation of similar depressions in more
posterior vertebrae.

17. The peripheral course of each of the eranial nerves is so constant that it would seem
to be of greater value for the determination of the segmental position of the nerve than the
apparent centers of origin of the fibers composing the nerve; it seeming more reasonable to
postulate varying composition, and condensations of ganglia or of centers of origin, than variations
in peripheral course. This being so, a nomenclature based on peripheral course seems much
preferable to one based on the character of the component fibers of the nerve or on the apparent
centers of origin of those fibers.

18. In all the Loricati examined, the ramus palatinus facialis either perforates the proötie
bridge or adjoining portions of the side wall of the proötic, and so passes from the cranial cavity
directly into the myodome. In all of the Craniomi examined this nerve first passes from the cranial
cavity into the trigemino-facialis chamber and then traverses that chamber to issue by its trigeminus
opening and so enter the myodome.

19. In all of the mail-cheeked fishes examined, excepting Dactylopterus, the nervus abducens,
in passing from the, cranial cavity to the muscle it innervates, either passes over the anterior
edge of the postpituitary portion of the proötie bridge or perforates that bridge near its anterior
edge. In Dactylopterus the nerve first passes from the cranial cavity into the trigemino-facialis
chamber and then issues from that chamber through its trigeminus opening to reach the muscle
it innervates. In Lepidosteus also the nerve has this latter course.

20. Cottus differs markedly, in many more or less important anatomical features, from the
other Loricati, and Dactylopterus differs still more markedly from the other craniomi; and if
craniological characteristies are of any especial value in phylogenetie determinations, it would
seem as if these two fishes could not be closely related to the other fishes of the mail-
cheeked group.

Palais de Carnoles, Menton, France.
February 27th. 1907.

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Gill, T., Note on the relationships of the Echeneidids. - vol. 5, Proc. U. S. Nat. Mus. for 1882.

— Classification of the mail-cheeked fishes. vol. .11, Proc. U. S. Nat. Mus. for 1888.

— Characteristics of the Dactylopteroidea, vol. 13. Proc. U. S. Nat. Mus. for 1890. :

— ÖOsteological characteristics of the family Hemitripteridae. vol. 13, Proc. U. S. Nat. Museum for 1891.

. — On the relations of the Cyclopteroidea. vol. 13, Proc. U. S. Nat. Museum for 1891.

Girard, C., Monograph of the Cottoids, Smithsonian Contributions to knowledge for 1851.

Gunther, A..C. L., Catalogue of the Fishes in the British Museum. vol. 2, London. 1860.

Handrick, K., Das Nervensystem und die Leuchtorgane des Argyropelecus hemigymnus. vol. 13,
Zoologica, 1901.

Herrick, C. J., The Cranial and First Spinal Nerves in Menidia. vol. 9, Journ. Comp. Neurology. 1899.

— Contribution on the Cranial Nerves of the Cod fish. vol. 10, Journ. Comp. Neurology.. 1900.

— On the Cranial Nerves and Cutaneous sense organs of the North American Siluroid Fishes. vol. 11, Journ.
Comp. Neurology. 1901.

Huxley, T. H., Manual of the Anatomy of Vertebrated Animals. New York, 1872.

Jaquet, M., Recherche sur l’anatomie et l’histologie du Siluris glanis. Nos. 3/4. Arch. des Sc. Med. for 1898.

Johnston, J. B., Morphology of the Vertebrate Head from the viewpoint of the functional divisions-of the
nervous systems. vol. 15, Journ. Comp. Neurology. 1905.

. — Cranial Nerve Components of Petromyzon. vol. 34, Morphologisches Jahrbuch. 1905.

Jordan & Evermann, The Fishes of North and Middle America, Bulletin 47 vol. 2, U. S. Nat. Museum
1898:

Jordan & Gilbert, Synopsis of the Fishes of North America. Bulletin 16, U. S. Nat. Museum. - 1883.

Kingsbury, TheStructure and Morphology of the Oblongata in Fishes vol. 7, Journ. Comp. Neurology. 1897.

Kupffer, C. von, Studien zur vergl. Entwickelungsgeschichte des Kopfes der Kranioten. Hft. 3, Die
Entwickelung der Kopfnerven von Ammocoetes Planeri. - München. 1895.

Kyle, H. M. On the presence of nasal secretory sac and a naso-pharyngeal communication in Teleostei,
with especial reference to Cynoglossus. vol. 27, Zoology, Journ. Linn. Soc. Lond. 1900.

— 21l —

07. Landacre, F. L., On the place of origin and method of distribution of taste buds in Ameiurus -melas:
vol. 17, Journ. Comp. Neurology 1907.
‘05. Locy, W., On a newly recognized nerve connected with the fore-brain in Selachians. vol. 26, Anatomischer
Anzeiger, 1905.
"84. MeMurrich, J. P., Osteology of Amiurus catus. Proc. Canadian Inst. 1884.
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"82a. — On the Structure and Development of the Skull in the Sturgeons. Phil. Trans. Roy. Soc. Lond, 1882.
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92. Pollard, H. B., On the Anatomy and Phylogenetie position of Polypterus. vol. 5, Zool. Jahrb. 1892.
’92/’%. Quain’s Elements of Anatomy, Edited by E. A. Schafer & G. D. Thane. 10th. Ed. London. 1892—%.
81. Retzius, G., Das Gehörorgan der Wirbeltiere, vol. 1., Stockholm, 1881.
99, Ridewood, W. G., On the relations of the Efferent Branchial Bloodvessels to the ‚‚Cirulus Cephalicus‘
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"84a. — 1I. Einige Bemerkungen über die Gehirnhaut der Knochenfische. vol. 9, Morph. Jahrb. 1884.
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31. Schneider, H., Über die Augenmuskelnerven der Ganoiden. vol. 15, Jenaische Zeitschr. 1881.
’84. de Sede de Lieoux, P., Recherches sur la ligne laterale des Poissons osseux. Paris. 1884.
’85. Shufeldt, H. W., Osteology of Amia calva. Rept. U. S. Fish Comm. 1885.
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04. — Osteology of some Berycoid Fishes. Proc. U. S. Nat. Museum. vol. 27, 1904.
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’01/’02. Supino, F., Richerche sul eranio dei Teleostei. I—IV. Roma. 1901/02.

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‘65. Traquair, R. H., On the Asymmetry of the Pleuronectidae, as elucidated by an examination of the Skeleton
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78. Vetter, B., Untersuchungen zur vergleichenden Anatomie der Kiemen- und Kiefermuskulatur der Fische.
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82. Wijhe, J. W. van, Über das Visceralskelett und ‘die Nerven des Kopfes der Ganoiden und von Ceratodus.
vol. 5, Nieder. Archiv. Zoologie 1882.

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‘00. Workman, J. S., Ophthalmie and Eye-musele Nerves in the Catfish. vol. 10, Journ. Comp. Neurology. 1900.

‚85. Wright, R., Hyomandibular Clefts and pseudobranch of Lepidosteus and Amia. Vol. 19, Journ. Anatomy
and Physiology. Lond. 1885.

’87/’'%. Zittel, K., Handbuch der Palaeontologie. Abt. I. Palaeozoologie, vol. 3, 1887—1890.

Index to Fishes etc, referred to.

Acanthophthalmus 11. 12. 195. 199.

Acipenser 23. 149. 202.

Albula 8. 9. 10. 13. 31. 201. 204.

Alepocephalus 63.

Amblystoma 53.

Ameiurus 63. 84. 86. 87. 91. 163. 195. 198. 199. 200.
201. 202. 203.

Amia 7—10. 12. 14. 18. 19. 21—28. 31. .39—41. 43—45,
41—53. 55. 60. 61. 64. 65. 72. 74. 82. 87. 88. 125.
157. 164. 168. 183—194. 200—202. 204—207.

Argyropelecus 27. 190. 207.

Aulostomi 201. 202.

Balistes 63.

Bathythrissa 12.

Batrachididae 195. 199.

Batrachus 74.

Barbus 38, 41. 42.

Belone 19-21. 63. 142. 204.

Berycidae 201.

Berycoidea 201.

Blennius 166. 195. 198.

Callionymus 195. 199.

Carangidae 201.

Carassius 63.

Cataphracti 201.

Catostomus 11.

Caularchus 195. 199.

Centriscus 199.

Ceratodus 202.

Chanos 12. 34. 207.

Characinidae 10. 19. 27. 37. 47. 51. 55—58. 61. 84. 207.

Chimaera 74.

Christivomer 25.

Chromidae 201.

Chrysophrys aurata 27. 202.

Citharinus 31.

Clupea 9. 12. 27. 63. 201.

Clupeidae 13. 63. 201.

Cobitis 11. 12. 41. 195. 199. 200.

Comephoridae 195. 199.

Conger 195. 199.

Cottidae 195. 198. 199.

Cottus oetodecimospinosus 1. 2. 15. 22. 23. 39. 41.
52—54. 75—81. 98—112. 119. 123. 124. 134. 156.
173. 178. 196. 198. 205—208.

Cottus scorpius 1. 11. 75. 76. 83..86.

Crenilabrus 27. 201.

Cromeriidae 195. 199.

Cyclopterus 195. 199.

Cyelothone 195. 199.

Cyprinidae 9. 11. 19. 27. 37. 38. 44. 47. 541. 55. 56.
58. 61. 110. 118. 178. 199. 200. 207.

Cyprinus 38.

Dactylopterus 1. 2. 7. 39.. 47. 51. 52. 54. 76.: 79.
80—83. 85—92. 113. 143. 152. 156182. 183. 190.
199. 200—202. 204--206. 208.

Dapedius 201.

Diodon 63.

Diplophysa 11. 12.

Discocephali 195.

Echeneis 195. 198.

Ectreposebastes 73.

Elops 8—13. 16. 24—27. 31. 38. 42. 201. 204. 205.

Engraulis 10.

Erythrinus 11. 26. 63.

ES0x2.92.105.195207229259 217 319.632 203:
Fistularıa 195. 199. 202.
Frog 192.

Gadus 27. 49. 76. 86. 87. 90. 105. 194. 195 —197. 199.
200— 203.

Galaxias 63. 198.

Galaxiidae 195. 198.

Galeus 202.

Gasterosteus 12. 14. 20. 22. 23. 27. 28. 41. 42. 48. 70.
195. 199. 203.

Ginglymodi 201.

Gobeisocidae 195. 199.

Gobiidae 195. 199. 201.

Gobius eruentatus 27. 199. 200. 201.
Gonorhynchus 12. 23. 31. 195. 199.
Gymnarchus 12. 28. 31. 63. 64. 163. 198.
Halecomorphi 201.

Hemitripterus 166.

Heptanchus 202.

Heterotis 198.

Hexanchus 202.

Hippocampus 198.

Hippoglossus 27.

Homaloptera 38. 41.
Hoplopleuridae 201.

Hoplostethus 27. 201.

Hydrocyon 31. 110.

Hyodon 693.

Labrax 27.

Labridae 201.

Lacerta 184. 191. 192.
Lepidosteidae 202.

Lepidosteus 7. 23. 45. 64. 183—192. 200—202. 205.
Lepidotrigla 1. 2. 47. 51. 54. 76. 79. 81—93. 124. 125.

129. 206. 207.
Lepidotus 201.
Leptobarbus 9.
Lophius 24. 25. 27. 195. 198. 200.
Macrodon 10. 12. 26. 205.
Macrourus 27.
Megalops 13. 31. 63. 201.
Menidia 37. 47. 76. 78. 79. 80. 831. 83 —91.
Mieropterus 27.
Misgurnus 11. 12, 195. 199.
Mormyridae 12. 63. 195. 198.
Mormyrops 31. 198.
Moxostoma 11.
Mugil 27.
Muraenidae 63. 199. 205.
Mustelus 202.
Necturus 192.
Nemachilus 11. 12. 195. 199.
Notopterus 12. 31. 63.
Ophidium 27.
Ophiodon 39. 40. 51. 52. 53. 54. 83.
Osteoglossum 23. 26. 63. 122. 195.
Otolithus 27.
Pantodontidae 195.
Pantodon 198.
Pediculati 195.
Perca 27.

214

Peristedion cataphractum 1. 2. 39. 136-156. 158.
163. 201. 203.

Petrocephalus 198.

Petromyzon 82. 83. 88.

Phractolaemidae 19.

Phractolaemus 69. 198.

Pleuronectes 53. 54. 86. 88. 90. 198.

Pleuronectidae 19.

Polyodon 206.

Polypterus 7. 23. 26. 64. 165. 188. 189. 190. 202. 204.
205. 206.

Pomatomus 27.

Rasbora 9.

Rhamphoeottidae 195. 199.

Rhombus 27. 54.

Ruvettus 27.

Salmo salar 9.
204.

Salmo trutta 25.

Salmonidae 201.

Sargus 202.

Saurocephalidae 201.

Saurus 201. 203.

Scaphyrhynchus 149.

Sciaena 27.

Sclerognathus 11. 12.

Scomber 6—8. 11—14. 16. 18. 22. 27. 30. 33. 36. 37.
39. 40. 41—47. 51. 52. 54. 66. 70. 71. 72. 79. 83. 84.
89..116.1212136.21232 14621572 17721875198 202

Scopelidae 201.

Scopelus 201.

Scorpaena porcus 1. 2. 3. 4. 5. 62.

Scorpaena scrofa 1. 2. 3-9. 95—102. 104—107.
109—112. 114—121. 123—127. 131. 133. 134. 135.
137. 138. 141. 142. 143. 145. 146. 147. 154. 155. 156.
1592.163.2164 168 u 17218 EI IT ODE IE OTE
198. 205. 206. 207.

Scorpaenichthys 109.

Seymnus 202,

Sebastes dactylopterus
125. 205.

Sebastodes 3. 4. 78. 9.

Siluridae 26. 64. 199. 201. 202. 205.

Silurus 27. 63. 105. 195. 199. 200. 202.

Siphonostoma 69.

Solea 54.

Sparidae 201. 202.

Sphyraena 24. 25. 27.

Stomiatidae 195. 199.

Stratodontidae 201.

18. 21. 24. 25. 26. 28. 31. 63. 195. 201.

1. 2. 9-98. 100. 106. 109.

Stylodontidae 201. 202.

Syngnathus 195. 198.

Tinca 27.

Trachurus 27. 201.

Trigla gurnardus 1. 83. 91. 93. 114. 123. 127. 128.
Trigla hirundo 1. 17. 39. 47. 51. 52. 54. 76. 7

86. 88. 90. 91. 93. 113-135. 136. 138—146. 148.

149. 154—156. 158. 177. 203. 205. 206. 207.
Trigla lineata 1. 118.

Trigla lyra 1. 2. 113. 128. 135—136. 148. 149, 203.

215

Trigla obscura 1.
Trigla pini 1. 128.
Triglopsis 27.

Triton 53.
Uranoscopidae 19.
Uranoscopus 27. 197.
Vomer 27.

Xiphias 202.
Xiphiidae 201. 202.
Zeus faber 27.

Aap
Ah
ah.fr
ANG
Ao
ART
art.h

art.mx.
art.pmx
AS
asc.mx.
asc.pmx
asc.v

BO

Explanation of Figures.

Index letters.

Adductor arcus palatinus.

Adductor hyomandibularis.

Foramen for the arteria hyoidea.

Angular.

Adductor opereuli.

Artieular.

Artieular process of the hyomandibular, or
corresponding process or facet on the skull.

Artieular process of maxillary.

Artieular process of premaxillary.

Alisphenoid.

Ascending process of maxillary.

ascending process of premaxillary.

Ascending process of vomer.

Basioceipital.

Basisphenoid.

Ciliaris brevis.

Ciliaris longus.

Dentary.

Dermo-ectopterygoid.

Dilatator groove.

Dilatator operculi.

External carotid foramen.

Ecetopterygoid.

Ecetethmoid.

Entopterygoid.

Epiotie (Exoccipitale, Sagemehl, Exoceipital,
Allis).

Extrascapular.

Exoceipital (oceipitale laterale, Sagemehl).

Facialıs canal through the hyomandibular.

Facialis foramen.

Facialis opening of
chamber.

Frontal.

Ciliary ganglion.

trigemino-facialis

Communis ganglion.

ggle
geli
gl
glfr
gp
gt

106

IOP
TOR.
LA

Extracranial glossopharyngeal ganglion.
Intracranial glossopharyngeal ganglion.
Nervus glossopharyngeus.
Glossopharyngeus foramen.

Profundus ganglion.

Trigeminus ganglion.

Sympathetie ganglion.

Extracranial vagus ganglion.
Intracranial vagus ganglion.
Hyomandibular.

Internal carotid foramen.

ist. to 11th. Infraorbital latero-sensory
organs.

Infraorbital latero-sensory canal.

Interopereular.

Ist. to Ath. Infraorbital bones.

Lachrymal.

Labe I—-V. Levator arcus branchialis externus of first

Labi?
LabiP

Lap

Lo
mef.fr
MET
met.pr.
mif.fr
MP
MX
mXx.p

NA

to fifth branchial arches.

Levator arcus branchialis internus, anterior
muscle.

Levator arcus branchialis externus, posterior
muscle.

Levator arcus palatinus.

Levator opereuli.

Foramen for mandibularis externus facialıs.

Mesethmoid.

Mesethmoid process.

Foramen for mandibularis internus facialıs.

Metapterygoid.

Maxillary.

Maxillary process of Palatine.

Nasal.

nasal aperture. Ir

nervus facialıs.

Nervus lineae lateralıis.

Nervus optieus.

Foramen for oceipital nerves.

Nervus olfactorius.

Olfactory foramen.

Opereular.

Ophthalmicus lateralis canal.

Opisthotie.

Palatine.

Parieto-extrascapular.

Palatinus facialıs.

Ist. to 11th. Preoperculo-mandibular latero-
sensory organs.

Premaxillary.

Pontinal.

Preopereular.

Postorbital.

Foramen for nervus profundus.

Proötie.

Parasphenoid.

Postfrontal.

Pterotic.

Quadrate.

Rostral.

Ramus communicans from trigeminus to
facıalıs.

Branch of oculomotorius to rectus internus
and rectus inferior.

Radix longa.

Explanation of

r.oi Branch of oculomotorıus to obliquus
inferior.

T.TS Branch of oculomotorius to rectus superior.

SCL Supraclavicular.

SOhTS Ist. to 6th. Supraorbital latero-sensory
organs.

so Supraoceipital.

soc Supraorbital latero-sensory canal.

SOP Subopereular.

SOR! ist. Suborbital.

SOR? 2nd. Suborbital.

SPH Sphenotic.

spoc Spina occeipitalis.

S.POP Suprapreopercular.

SSC Suprascapular.

ste Supratemporal latero-sensory canal.

sta“ ist. to 2nd. Supratemporal latero-sensory
organs.

SY Sympleectie.

Tda Transversus dorsalis anterior.

tfe Trigemino-facialis chamber.

t.ir Trigeminus foramen.

tgr Temporal groove.

to Trigeminus opening‘ of trigemino-facialis
chamber.

vfr Vagus foramen.

vo Vomer.

Plates.

The figures used for illustration were to have been made from the specimens used for the descriptions,

but as those speecimens had been more or less injured by repeated handling, other specimens were specially

prepared for the drawings.

minor details.

Big 1.
Its 2%
Fig. 3.
Fig. 4.
Fig. 5.
Iren (0%
Rio 37.
Fig. 8.
Big. 9.
Fig. 10.
Fig. 11.

Zoologica.

Balrantzesle

Lateral view of the skeleton of the head x 1Y,.

Dorsal view of the same x 1Y..

The figures will accordingly be found to differ from the descriptions in certain

Scorpaena scrofa.

Dorsal view of the skull with the right nasal bone in place x 1Y,.

Ventral view of the same x 1Y,.
Lateral view of the skull x 1Y,.
Median view of a bisected skull x 1Y,.

Bilractrez lie

Scorpaena scrofa.

Dorsal view of the skull with the dermal bones removed, excepting the right postfrontal and supra-

scapular x 1/,.

Posterior view of the same with right suprascapular in place x 1),.

Orbital view of the brain case x 1Y,.
Dorsal view of the vomer x 1Y,.

Lateral view of the left hyomandibulo-palato-quadrate apparatus x 1Y,.

Heft 57.

189]
[e2)

Fig.

Fig.

Fig.

Fig.

Fig.

Fig.
Fig. A
Fig.

Fig.

D'

D'

je en je
am woD

>

20:

SD DD DDD
Sn

>
oo 8 SI

Dr

— 218 —

Median view of the right hyomandibulo-palato-quadrate apparatus with the preopereular attached x 1/,.
Lateral view of the left maxillary x 1Y,.

Median view of the head of the right maxillary x 1Y,.

Lateral view of the brain case, showing the insertions of the muscles x dee

Lateral view of the left premaxillary x 1Y,.

Median view of the head of the right premaxillary x 1,.

Ventral view of the frontal x 1Y,.

Diagrammatic view of the latero-sensory canals x 1.

Pillatter Ile Serbrasıtress daet vikorp.terus FandSieorp alemearsıer.otfa.

Dorsal view of the skull of Sebastes dactylopterus with both postfirontals and the left nasal, extra-
scapular, suprascapular and supraclavicular attached x 2.

Lateral view of the same with postfrontal attached x 2.

Ventral view of the same x 2.

Posterior view of the same x 2.

Lateral view of the left premaxillary x 2.

Median view of the head of the right premaxillary x 2.

Lateral view of the left maxillary x 2.

Median view of the head of the right maxillary x 2.

Ventral view of the brain of Scorpaena serofa with the eranıal and oceipital nerves x 4.

PlatesIV.: Cottusoctodecimospinosus.

Lateral view of the skeleton of the head x 2.

Dorsal view of the skull with left nasal, postfrontal, extrascapular, suprascapular and supraclavicular
attached x 2.

Ventral view of the skull x 2.

Lateral view of the same x 2.

Median view of a-bisected skull x 2.

Median view of the right hyomandibulo-palato-quadrate apparatus with preopereular attached x 2.

Lateral view of the left hyomandibulo-palato-quadrate apparatus, without preopereular x 2.

Median view of the right lachrymal bone x 2.

Posterior view of the skull x 2.

Diagrammatic view of the latero-sensory canals x 1/,.

PiliatzesıV. STrireilahirun.dxo:

Lateral view of the skeleton of the head x 1.

Dorsal view of the same x 1.

Lateral view of the oceipital region of the skull and the first four vertebrae x 2.

Posterior view of the skull x 1.

Dorsal view of the same x 1.

Ventral view of the same x 1.

Lateral view of the same with supraclavicular attached x 1.

Median view of a bisected skull x 1.

Dorsal view of the skull of Trigla gurnardus with the dermal bones removed x 1Y,.

Lateral view of the left maxillary of Trigla hirundo x 1.

Median view of the head of the right maxillary x 1.

Lateral view of the left premaxillary x 1.

Median view of the head of the right premaxillary x 1.

Lateral view of the infraorbital bones of a specimen in which there were four of these bones x 1.
Lateral view of the left hyomandibulo-palato-quadrate apparatus x 1.

Median view of the right hyomandibulo-palato-quadrate apparatus with the preopereular attached x 1.

8-

Fig.

S-

[11
or

[us Bus
8 @ I

[op]
(=)

[oPieriioriforiker)
ARERBE

[er)
[or

[oriKer)
>25

en)

oO

SIeSy aag
nz

[e%

nn X
Ser

Rn
&

[0 0)
(de)

=

Plate VI. Peristedion cataphractum.

Dorsal view of the skeleton of the head x 1\,.

Lateral view of the skeleton of the head x 1/,.

Dorsal view of the skull x 2.

Ventral view of the skull x 2.

Lateral view of the skull x 2.

Ventral view of the left lachrymal x 2.

Lateral view of the left hyomandibulo-palato-quadrate apparatus x 2.
Median view of the right hyomandibulo-palato-quadrate apparatus with the preopereular attached x 2.
Dorsal view of the parasphenoid x 2.

Lateral view of the same x 2.

Dorsal view of the left premaxillary x 2.

Dorsal view of the left maxillary x 2.

Posterior view of the skull x 2.

Diagrammatice view of the latero-sensory canals x 1Y,.

Plate VII. Dactylopterus volitans.

Dorsal view of the skeleton of the head, with the bones on the dorsal surface of the head filed down on
the right side, so as to show the course of the latero-sensory eanals x 1Y,.

Ventral view of the skull x IR

Lateral view of the skeleton of the head x 1Y;.

Ventral view of a part of the roof of “the skull x 14,.

Posterior view of the skull with the hind ends of the extrascapulars, suprascapulars and supraoeceipital
eut off x 2.

Orbital view of the brain case x 2.

Dorsal view of the right epiotie x 2.

Cerebral view of the left proötie x 2.

Dorsal view of the alisphenoid x 2.

Ventral view of the alisphenoid x 2.

Plate VIII. Dactylopterus volitans and Trigla hirundo.

Dorsal view of the parasphenoid of Dactylopterus volitans x 2.
Dorso-mesial view of the right sphenotie and postirontal x 2.

Dorsal view of the left premaxillary x 2.

Dorsal view of the left maxillary x 2.

Dorsal view of the basioceipital x 2.

Dorsal view of the right exoceipital x 2.

Lateral view of the left hyomandibulo-palato-quadrate apparatus with the preopereular attached x 1\/;.
Median view of the left palatine x 2.

Median view of the right hyomandibular x 2.

Diagrammatic view of the latero-sensory canals of Dactylopterus x 1Y;.
Diagrammatie view of the latero-sensory canals of Trigla hirundo x 1.

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51.

. Verzeichnis. der Bisher a Hefte der Zoologica:
Di ir (Fortsetzung.)

= Braem, F, ni ‚geschlechtliche Entwicklung von Plumatella fungosa. Mit 3 Tafeln. 1897. 36,—,
24. Thiele, J., Studien über pazifische Spongien, 2 Teile mit 13 Tafeln und 1 Holzschn. 1898. 48,—.

Rt 2.

27. _ Pagenstecher, A., Die Lepidopterenfaunad.Bismarck-Archipels. I. Die Tagfalter. M.2kol. Taf. 1899. 28,—.

'Stoller, J. H., On the organs of respiration of the oniscidae. 1899. ‘Mit 2 Tafeln. 7,—.
Wasmann, E., S. J., Die psychischen Fähigkeiten der Ameisen. 2. Aufl.. 1908, ‘Mit 5 Tafeln. 9,60.

Miltz, O., Das Auge der Polyphemiden. Mit 4 kolor. Tafeln. 1899, 18,—.

Pagenstecher, A., Die Lepidopterenfaunad,Bismarckarchip. II. Die Nachtfalter. M.2kol. Taf. 1900. 38,—.
Müller, G. W., Deutschlands Süßwasser-Ostracoden. Mit 21 Tafeln. 1900. 60,—, ;
Michaelsen, W., Die holosomen Ascidien des magalhäensisch-südgeorg. Gebiets. Mit 3 Taf. 1900. 24,—.
Handrick, K.,7.Kenninis d. Nervensyst.u. d. Leuchtorg. v. Argyropelecus hemigymnus. M, 6 Taf. 1901. 28,—.
Heymons, R., Die Entwickelungsgeschichte der Scolopender. Mit 8 Tafeln. 1901. 52,—.
Woltereck, R., Trochophora-Studien. I. Mit 11 Tafeln und 25 Textfiguren. 1902. 40,—
Bösenberg, W., Die Spinnen Deutschlands. Mit 43 Tafeln, 1901-1903. „95, —.

Stromer v. Reichenbach, E., Die Wirbel der Landraubtiere, ihre Morphologie und svstematische Be-
deutung. Mit 5 Tafeln. 1902. 48,—.

Leche W., Entwicklungsgesch. d. Zahnsystems .d. Säugetiere. II. Phylogenie. H. 1: Erinaceidae. M. 4 Taf.
und 59 Textfiguren. 1902. 24,—.

Illig, K. G., Duftorgane der männl. Schmetterlinge. Mit 5 Taf. 1902. 24,—
Schauinsland, H., Beitr. z. Entwickelungsgesch. u, Anatom. d. Wirbeltiere I. II. III. M, 56 Tat. 1903. 80,—.

Zur Strassen, Otto L., Geschichte der T-Riesen von Ascaris megalocephala. Mit 5 Tajeln u. 99 Text-
figuren. 1903—1906. -76,—.

Müller H., Beitrag z. Embryonalentwickl. v. Ascaris megalocephala. Mit 2 Taf. u. 12 Textfig, 1903. 36,—.

Börner, C., Beiträge zur Morphologie der Arthropoden. I. Ein Beitrag zur Kenntnis der Pedipalpen.
Mit 7 Tafeln und 98 Textliguren. 1904. 64,—.

Escherich, K., Das System der Lepismatiden. Mit 4 Tafeln und 67 Textfiguren. 1905. 42,—.

Daday, E. von, Untersuchungen über die Süßwasser-Mikrofauna Paraguays. Mit einem Anhang von
W. Michaelsen. Mit 23 Tafeln und 2 Textfiguren. 1905. 80,—.

Fischer, G., Vergleichend:anatomische Untersuchungen über den Bronchialbaum der Vögel. Mit 5 Tafeln
und 2.Textfiguren. 1905. 28,—.

.. Wagner, W., Psychobiologische Studien an Hummeln. Mit 1 Tafel und 136 Textfiguren. 1906—1907. 60,—.

Kupelwieser, H., Untersuchungen über den feineren Bau und die Metamorvhose des Cvohonautes.
"Mit 5 Tafeln und 8 Textfiguren. 1906. 24,—.

Borcherding, Fr., Achatinellen-Fauna der Sandwich-Insel Molokai. Mit 10 ua und 1 Karte von
Molokai. 1906. ı75,—.

_ Leche, W., Zur Entwicklungsgeschichte des Zahnsystems der Säugetiere. II. Phylogenie. H. 2: Centetidae,
Solenddontidae und Chrysochloridae. Mit 4 Tafeln und 108 Textfiguren. 1907. 40,—.

Schwabe, J., Beiträge zur Morphologie und Histologie der tympanalen Sinnesapparate der Orthopteren.
-Mits5YTafeln und 17 Textabbildungen. 1906. 50,—.

Lävß, Ad., Vergleichende Anatomie der Spechtzunge. Mit 6 Tafeln und 13 Textfiguren. 40,—.
. Braem,, F., Die geschlechtliche Entwickelung von Fredericella sultana nebst Beobachtungen über die

MT weitere Lebensgeschichte der Kolonien. Mit 7 Tafeln und 1 Textfigur. 1908. 32,—.
wert "Hilzheimer, M., Beitrag zur Kenntnis der nordafrikanischen Schakale, nebst Bemerkungen über

deren Verhältnis zu den Haushunden, insbesondere nordalrikanischer und altägyptischer Hunderassen.
Mit 10 Tafeln und 4 Tabellen. 36.—

4.. Kennel, J. v., Die paläarktischen Tortrieiden. Eine monographische Darstellung. Mit 24 Tafeln,

einer Stammtafel und mehreren Textfiguren. Lieferung 1. 100 Seiten mit 6 Tafeln, für die Abon-
nenten auf die „Zoologica‘“ 20,—, für die übrigen Besteller 24,—.

55. Kahle, W., Die Paedogenesis der Cecidomyiden.; Mit 6 Tafeln und 38 Textliguren. 42,—.
„ 56. Thiele, Joh., Revision des Systems der Chitonen. 1. Teil. Mit 6 Tafeln und 5: Textfiguren. 28,—.

(Der II. Teil mit 4 Tafeln befindet sich im Druck.)

—

Heft 1.

”

.Kohl, ©., Rudimentäre Wirbeltieraugen. Nachtrag. 1895. 12,—.

»N.Schmeil, ©., Deutschlands freilebende Süßwasser-Copepoden. Nachtrag’zu den Familien der Cyclopiden

Verzeichnis der bisher erschienenen Hefte der Zoologica:

Ohun, C., Die pelagische Tierwelt in größeren Meerestiefen und ihre Beziehungen zu der‘ Oberflachen- Kst
fauna. Mit 5 farb. Doppeltafeln. 1880. 20,—.

Strubell, Ad., Untersuchungen über den Bau und die Entwicklung des Rübennemätoden Hoterodern,
Schachtii- Schmidt... Mit 2 z. T. farb. Tafeln. 1888.” 10,—. £

Vanhöffen, E., Untersuchungen üb. semäostome u. rhizostome Medusen. M. 6farb. Taf. ARarte 1e8& Ph

Heckert, G. A., Leucochloridium Paradoxum. Monograph. Darstellung der Entwicklungs- und Lebens:
geschichte des Distomum macorostomum. Mit 4 z. T. farb. Tafeln, 1889. 20,—.

Schewiakoff, W., Beiträge zur Kenntnis der holotrichen Giliaten. Mit 7 farb. Tafeln. 1889. 32, BR

Braem, Fr., Untersuchungen über die Bryozoen des süßen Wässers! Mit 15 2. T. farb. aaa und
zahlreichen Illustr. im Text. 1890. 80,—. f

Kaiser, Joh., Beiträge zur Kenntnis der Anatomie, Histologie und Entwicklungsgeschichte der Acantor-
cephalen. 2 Teile. Mit 10 Doppeltafeln. 1891—92. 92,—.

Haase, E., Untersuchungen über die Mimiery auf Grundlagen eines natürlichen Systems der Papilioniden.
2 Bände. Mit 14 farb. nach der Natur gezeich. u. lithogr. Tafeln. 1891—1892. 90,— 3

Herbst, C©., Beiträge zur Kenntnis der Chilopoden. Mit 5 Doppeltafeln, 1891. 24,—.
Leichmann, &., Beiträge zur Naturgeschichte der Isopoden. Mit 8 Tafeln. 1891. 24,—
Schmeil, ©., Deutschlands freilebende Süßwasser-Copepoden. I. Cyclopidae. Mit 8 z. T..farb. Tafeln
und 3 Illustr. im. Texte. 1892, 54,—.
Frenzel, Joh., Untersuchungen über die mikroskopische Fauna Argentiniens. I. Die Protozoen.
T. Lig. 1—4. Mit 10 farb. Tafeln. 1892. 56.—.
Kohl, ©., Rudimentäre Wirbeltieraugen. I. Mit 9 farb. Doppeltafeln. 1892. 73,—.
Kohl, ©., Rudimentäre Wirbeltieraugen. II. Mit 6 farb. Doppeltafeln. "1893. .62,—.

Schmeil, O., Deutschlands freilebende Süßwasser-Copepoden. IT. Harpactieidae. Mit 8 z. T. farb. Tafeln
und Illustr. im Texte. 1893. 40,—.

Looss, A., Die Distomen unserer Fische und Frösche. Neue Untersuchungen über Bau und Entwicklung
des Distomenkörpers. Mit 9 farb. Doppeltafeln. 189%. _82,—.

Leche, W., Zur Entwicklungsgeschichte des Zahnsystems der Säugetiere, zugleich eın Beitrag zur Stammes- 7
geschichte dieser Tiergruppe. I. Ontogenie, Mit 19 Tafeln und 20 Textfiguren. 1895. 64,—.

Nagel, W. A., Vergleichend physiologische und anatomische Untersuchungen über den Geruchs- und Ge-
schmackssinn und ihre Organe mit einleitenden Betrachtungen aus der allgemeinen NEIBIAECHERENE Sinnes-,
physiologie. Mit 7 z. T. farb. Tafeln. 1894. 42, — n

Ohun, O., Atlantis. Biologische Studien üb. pelagische Organismen. M. 12Doppeltaf. u. 8 einf. Taf. 1896. 128,—.

Zoologische Ergebnisse der v. d. Ges. für Erdkunde in Berlin ausgesandten Grönlandsexpedition. 1) Dr.
RB: Vanhöffen: Untersuchungen üb. Arachnactis albida Sars. 2) Ders.: Die grönländ. Ctenophoren. M.A Taf.
7,—. 3) Dr. H. Lohmann: Die Appendikularien der Expedition, Mit 4 Tafel. 4) Prof. Dr. K. Brandt: Die
Tintinnen. Mit 1 Tafel. Zusammen 12,—: 5) Dr. H. Lenz: Grönländische Spinnen. Mit 9 Holzschnitten.
6) Dr. Kramer: GrönländischeMilben. M.3 Holzschn. 7) Dr..Sömmer: Drei Grönländerschädel. M. 1 Taf.9,—.
8) E. Rübsaamen: Mycetophiliden ete. Mit 2 Tafeln: 9) W. Michaelsen: Grönländische Anneliden, 12,—

Schmeil, ©., Deutschlands freilebende Süßwasser-Copepoden, III. " Centropagidae. Mit’12 2. T. farb.
Tafeln und Illustrationen im Text. 1896. . 50,—.

und Gentropagiden. Mit 2 Tafeln." 1898. 12,—
Piersig, R., Deutschlands Hydrachniden. Kornplett. Mit 51.2. T. farb. Tafeln. 132,—.