all the mail-cheeked fishes examined, excepting Cottus, and there appears as a jugular groove on th e
outer surface of the prepared skull. In Cottus the outer wall of th e space is of hone and th e inner
wall largely of membrane, the space there appearing as a recess on th e inner surface of the prepared
skull. The outer wall of th e space, primarily of membrane, is invaded to a different extent, in different
fishes, by th e neighbouring bones, th u s giving rise to greatly varying conditions.
16. The myodome of fishes is primarily a subpituitary space th a t is connected with the
o rbit of either side, or with th e orbital region, by a canal th a t transmits th e p itu ita ry vein.
Secondarily this subpituitary space acquires a wide communication with th e orbits, th e primal
cause of this secondarily acquired communication apparently being a deepening of th e hind ends
of th e orbits due to a marked enlargement of th e eyeballs. Following th is ’ deepening .of th e
orbits, certain of th e eye-muscles of either side enter th e p itu ita ry canal and, enlarging th a t
canal, finally wholly break down th e wall th a t separates the orbits from the subpituitary space.
I t seems possible th a t th e subpituitary space may represent th e conical depression on the
anterioT surface of the body of a vertebra, th e later acquired, posterior, or basioccipital extension
of th e myodome th en possibly being due to th e assimilation of similar depressions in more
posterior vertebrae.
17. The peripheral course of each of th e cranial nerves is so constant th a t it would seem
to be of greater value for th e determination of th e segmental position of th e nerve th a n the
apparent centers of origin of th e fibers composing th e nerve; it seeming more reasonable to
postulate varying composition, and condensations of ganglia or of centers of origin, th a n variations
in peripheral course. This being so, a nomenclature based on peripheral course seems much
preferable to one based on th e character of th e component fibers of the nerve Or on th e apparent
centers of origin of those fibers.
18. In all th e Loricati examined, the ramus palatinus facialis either perforates th e prootic
bridge or adjoining portions of th e side wall of th e prootic, and so passes from the cranial cavity
directly into th e myodome. In all of th e Craniomi examined this nerve first passes from the cranial
cavity into th e trigemino-facialis chamber and th en traverses th a t chamber to issue by its trigeminus
opening and so enter th e myodome.
19. In all of th e mail-cheeked fishes examined, excepting Dactylopterus, th e nervus abducens,
in passing from th e cranial cavity to th e muscle i t innervates, either passes over th e anterior
edge of th e p ostpituitary portion of th e prootic bridge or perforates th a t bridge near uts anterior
edge. In Dactylopterus the nerve first passes from th e cranial cavity into th e trigemino-facialis
chamber and then issues from th a t chamber through its trigeminus opening to reach the muscle
it innervates. In Lepidosteus also the nerve has this la tte r 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 characteristics are of any especial value in phylogenetic determinations, it would
seem as if these two fishes could not be closely related to th e other fishes of the mailcheeked
group.
Palais de Carnoles, Menton, France.
February 27th. 1907.
Bib l io g r a p h y .
’33/'43. A g a s s iz , L., Recherches sur les poissons fossiles, Neuchatel. 1833/43.
’05. Al l e n , W. F., The Blood vascular system of the Loricati, the mail-cheeked fishes, vol. 7, Proc. Washington
Academy of Sciences. 1905.
’89. Al l i s , Edward Phelps, jr., The Anatomy and development of the Lateral Line System in Amia calva. vol. 2,
Journ. of Morphology. 1889.
'97a. — The Cranial Muscles, and Cranial and first spinal nerves in Amia calva. vol. 12, Journ. of Morphology. 1897.
b. — The Morphology of the Petrosal bone and of the Sphenoidal region of the Skull of Amia calva. vol. 1,
Zoological Bulletin. 1897.
’98. — The Morphology of Certain of the Bones of the Cheek and Snout of Amia calva. vol. 14, Journ. of Morphology.
1898.
'00a. — The Lateral Sensory Canals in Polypterus bichir. vol. 17, Anat. Anz. 1900.
b. — The Premaxillary and Maxillary Bones and the Maxillary and Mandibular Breathing Valves of Polypterus
bichir. vol. 18, Anat. Anz. 1900.
c. — The Pseudobranchial Circulation in Amia calva. vol. 14, Zool. Jahrb. Abt. f. Anat., 1900.
'01. — Lateral Sensory Canals, the Eye-Muscles and the peripheral distribution of certain of the Cranial Nerves
of Mustelus laevis. . vol. 45, Q.J.M.S., Lond. 1901.
’03. — The Skull and the Cranial and first Spinal Muscles and Nerves in Scomber scomber, vol. 18. Journ. of
Morphology. 1903.
’04. — The Latero-Sensory Canals and Related Bones in Fishes, vol. 21, Internat. Monats. f. Anat. u. Phys. 1904.
'05; B i n g & B u r c k h a r d t , Das Centralnervensystem von Ceratodus Forsteri. vol. 4, Denkschrift. der med.-
naturw. Ges. zu Jena. 1905.
'04. B o u l e n g e r , G. A., Synopsis of Suborders and Families of Teleostean fishes, vol. 13, (ser. 7) Ann. Mag.
Nat. Hist. 1904.
'95. Br i d g e , T. W., On Certain Features in the Skull of Osteoglossum formosum. P.Z.S. *Lond. 1895.
'00. — The Air-bladder and Auditory Organ of Notopterus borneensis. vol. 27, Zoology, Journ. Linn. Soc. Lond. 1900.
'84. Br o o k s , H. St. J., Osteology and Arthrology of the Haddock, vol.- 4. Proc. Roy. Soc. Dublin: 1884.
'56. B r u h 1, C. B., Osteologisches aus dem Pariser Pflanzengarten. Wien. 1856.
'91. — Zootomie aller Tierklassen. Lief. 5, 23 u. 24. Wien. 1.891.
'98. Cl a p p , C. M., Lateral Line System in Batrachus tau. vol. 15, Journ. of Morphology. 1898.
'06. C o g h i 11, G. E., Cranial Nerves of Triton taeniatus. vol. 16, Journ. Comp. Neurology. 1906.
'96. Col e, F., On the Cranial Nerves of Chimaera monstrosa, with a discussion of the Lateral Line System and
of the Morphology of the Chorda tympani. vol. 38, T. R. S. Edin. 1896.
98. — Structure and Morphology of the Cranial Nerves and the Lateral Sense Organs of Fishes, with especial
reference to the genus Gadus. vol. 7, Zoology, Trans. Linn. Soc. Lond. 1898.
'01. & Johnstone, J., The Plaice (Pleuronectes). vol. 10, Rept. of the Lancs. Sea Fisheries for 1901.
'93. C o 11 i n g e, W. E., The Lateral Canal System of Lepidosteus osseus. vol. 8, Proc. Birmhm. Philos. Soc. 1893.
'71. Cope , E. D„, Observations on the Systematic Relations of the Fishes. American Naturalist for 1871.
Extract in vol. 8, Zool. Record (pp. 93 — 94) for 1871.
Zoologica. Heft 57. 27