Table of Arrangement.- 
■FISHES. 
Dermopteres. 
108 
Sub-order A. — Apodal Malacopteres, or Serpentiform 
Apodals. 
In tlie ensuing pages the Primary Groups of Fishes 
will be ranged in the following orders : — 
TABLE OP ARKANGEMENT. 
I. Order. — Dermopteres (Owen), equivalent to the 
Myzontes of Agassiz, who considers them to hold the 
rank of a Class in the Vertebral Branch of Animals, 
Sub order A. — Pliaryngdbranchs or Cirrlwstomes, 
represented only by the Lancelots, which Agassiz 
surmises to be merely embryos of more highly 
organized fishes. 
Sub-order B. — Marsipobranclis (sacculated gills), or 
Cyclostomes (round mouths), called also Suchers. 
The next four orders belong to the Fishes proper of 
Agassiz, and are considered by him to constitute a class, 
divisible into Ctenoids and Cycloids : — 
II. Order. — Anacanths (no spinous fin-rays) having shut 
swim-bladders, and no radiated or fusiform bone cor- 
puscles in their skeletons. 
Sub-order A. — Helmichthyans or Tape-Jishes of 
Kblliker. 
“ B. — Apodal Anacanths. 
“ C. — -Thoracic Anacanths. 
“ D. — Heterosomes (Bonaparte), Dissimilar 
sides, or Flat-fish. 
“ E . — Colacides, Parasites or Ship-stayers. 
III. Order. — Pharyngognaths, whose right and left inferior 
pharyngeal bones are confluent, forming one piece. 
Their skeletons are destitute of bone corpuscles. 
Sub-order A. — Malacopterygian Pharyngognaths. 
“ B. — Acanthopterygian Pharyngognaths. 
IV. Order. — Acanthopteres, with ossified endo-skeletons 
without bone-corpuscles ; one or more anterior rays of 
the fins, especially of the ventrals, unjointed or indexible 
spines. Ventrals more generally situated in the thoracic 
or guttural regions ; swim-bladders closed. 
Sub-order A. — Ctenoids (Owen). 
“ B. — Cycloids (Owen), Scomberoid-scaled 
fishes. 
V. Malacopteres or Ph ysostomes, have open air-bladders, 
flexible, articulated fin-rays, and most generally true 
bony structure in their skeletons. 
“ B. — Abdominal Malacopteres. 
The Ganoids, as an order of vertebrals in the usual 
acceptation of the name, consist mostly of palseozoic 
fishes, and have comparatively few existing representa- 
tives. Professor Owen enumerates their essential char- 
acters, as they appear in fossil remains, in these words 
“ Endo-skeleton in some osseous, in some cartilaginous, 
in some partly osseous, partly cartilaginous ; exo-skeleton 
formed by enamelled bones ; fins usually with the first 
ray a strong spine.” 
Agassiz ranks them as the third class of vertebrals, 
and includes in the class the six following orders, but 
the first three merely provisionally, and dependent on 
further investigation for their true position in his system. 
VI. Order. — Sildroids (Agassiz). 
VII. Order. — Lophobranchs, or fishes with tufted gills. 
VIII. Order. — Plectognaths, named from the confluence or 
union by indented suture, of the right and left halves 
of the upper-jaw and mandible respectively. 
This structure of the jaws is not, however, altogether 
confined to this order. 
IX. Order. — Acipenseroids, or Sturionidans. 
X. Order. — Sadroids (Agassiz), or Lizard-Fishes. 
XI. Order.— C cELACANTHs (Agassiz), or Hollow Spines. 
A palaiozoic order which became extinct before the 
tertiary epoch. The dermal spines were ossified only 
externally, and are found hollow in the fossil state. 
The vertebral column ends in a prolonged appendage 
which separates the upper caudal lobe from the under 
one, as in some few existing fishes. 
The fourth class of Vertebrals, according to Agassiz, 
is composed of Selachians, a term which is equivalent 
to that of Plagiostomes (oblique mouths) of Dumeril. 
It embraces the three succeeding orders : — 
XII. Order. — Holocephalids or Chimasra: of Agassiz, 
XIII. Order. — Galeodes or Sharks of Agassiz. {Squali or 
Haijische of Muller and Henle.) 
XIV. Order. — Batides (Agassiz), Rays and Skates of other 
ichthyologists. Raice or Rochen of Muller and Henle. 
XV. Order. — Protopteres of Owen, an osculant form 
between Fishes and Keptiles, considered by some 
zoologists to be Amphibians, llchthyodi of Agassiz.) 
OiiDER I.— DEEMOPTERES. 
Pai,a:ontologists have by successive discoveries car- 
ried back the first appearance of Fishes to an early 
period in the formation of the crust of the earth ; and 
Professor Agassiz is of opinion, that it would not be 
difficult to show on physiological grounds, that their 
presence in primaeval oceans dates contemporaneously 
with that of the Radiata, Mollusca, and Articulata ; 
the plan of structure and means of subsistence of these 
three great types of the animal kingdom, constituting 
with the Vertebrals a mutually dependent system. 
There is, however, as yet no unequivocal evidence of 
fossil fishes below the newer silurian beds. The earliest 
remains of fishes have an embryonic character in the 
position of the mouth on the ventral aspect of the 
head, in the heterocercal caudal fin, in the absence of 
a hard internal skeleton, and in other parts of structure, 
which, as far as they can be made out, seem not to 
have been so highly developed as in the modern osseous 
fishes. The Dermopteres have a more decidedly em- 
bryonic aspect than any of the other existing groups of 
fishes. No remains of them have been identified in 
the palaeozoic strata, either because they were not early 
creations, or because the softness of their textures mili- 
tated against their preservation, so as to be recognizable 
in indurated deposits diat have been subjected to the 
action of heat, great pressure, and sundry displace- 
ments. Ichthyologists now concur in ranking this order 
at the bottom of the scale of fishes, and consequently, 
as the lowest of the vertebrals ; but though in common 
parlance the Dermopteres are said to be comparatively 
feebly organized, they are not imperfect, being in every 
way adapted to fill their station in nature, and to per- 
form their allotted functions. 
The essential characters of the group, as drawn by 
eminent zoologists, are the want of the lateral pairs 
of fins representing hands and feet, that is, they are 
abrachial and apodal, with long vermiform bodies; 
their internal skeleton is not ossified, being either 
cartilaginous, or merely membranous: their external 
skeleton does not take even the consistency of scales, but 
remains in the condition of soft, muciferous skin ; and 
the fin-rays and teeth when present are muco-dermoid 
