160 Sturionidans. FISHES. Aciprnseroids. 
only genus is Orthagoriscus or Orthragoriscus, of which 
The genera are — Tetraodon; Physogaster (Muller); Chdo- 
two species frequent our seas, viz., the Short and the 
nodon (id.) ; Cheilichthys (id.) ; and Arothron (id.). 
Oblong Molebut {Orth, mola and ohlongus). 
Some of these groups have no olfactory sac, or even 
The Tetrodonts, forming a family or suh-family 
depression, the nerve of smell being expended on a 
of some Ichthyologists, is equivalent to the genus Tet- 
solid, imperforate barbel. 
raodon of Linnaeus and Cuvier. They have their 
In the Triodonts the mandible is undivided, as in 
gorget-shaped jaws, in which the teeth are incorporated. 
the Diodonts, while the upper jaw has a mesial suture 
divided above and below by serrated, mesial sutures. 
as in the Tetrodonts. An immense dewlap is sustained 
forming four dental masses, whence the name. The 
in front by a very large bone representing the pubics, 
skin is partially and variously armed by spines, which 
and resembling the same parts in some Ba'istids. The 
are smaller than those of the Diodonts, and in an 
fins are like those of the Diodonts, and the asperities of 
electric species are wholly absent. Some genera 
the body and dewlap resemble those of the Tetrodonts. 
have inflatible bodies ; others do not possess the 
A single species from the Indian seas is called Triodon 
power of inflation, and have a moderately elongated 
bursarius, and is described by Lesson and Garnot in 
form. 
their ichthyology of the voyage of Duperrey. 
GANOIDS. 
Typical ganoid scales have generally a rhomboid or 
osseous fishes. Several Ganoids have an accessory 
quadrangular outline, with a smooth, shining coating 
branchial organ in form of an opercular gill, which 
of enamel. They are seldom rounded, and rarely 
differs from a pseudobranchia, and may co-exist with 
imbricated, being more commonly arranged in oblique 
it. Many have spout-holes {spiracula or blowing- 
rows whose edges touch ; but each scale is secured to 
holes) like the Plagiostomes. In the arterial bulb or 
the one that precedes it bj^ a hinge-like process of its 
stem there are several rows of valves. The eggs are 
anterior corner. Like ordinary scales, the ganoid plates 
generated in ovisacs and discharged through oviducts.’ 
are developed in follicles, but their epidermal coating 
No decussation {chiasma) exists between the optic 
is so very thin and so closely adherent as to be nearly 
lobes, but merely a lateral cohesion. The swim-blad- 
imperceptible. Muller sums up his view of the ganoid 
ders have pneumatic tubes ; the skeleton is bony, or 
character in the following terms : — Fishes provided 
partly cartilaginous ; and the ventral fins are situated on 
with tabular and angular or roundish enamelled scales. 
the abdomen. According to the researches of Kblliker, 
or with bony plates, or with a perfectly naked skin ; 
tlie skeletons of the Plectognaths and Lophobranchs 
liaving fins frequently, but not always, sustained in 
are destitute of bone corpuscles, but those of the other 
front by a single or double row of spiny plates, techni- 
orders enumerated as Ganoids by Agassiz contain these 
cally named fulcra ; and a caudal fin involving in its 
organisms. All the above characters do not exist in 
upper fold the extremity of the vertebral column, which 
every Ganoid ; and the essential parts of structure are. 
may continue to the end of the fold. The free gills are 
according to Muller, several rows of valves in the arterial 
placed in an operculated cavity, like those of the true 
bulb, free operculated gills, and abdominal ventral Jim. 
Order IX.— S T U R I ON I D A N S. 
intestine. In the genus Scaphirhynchus the tail is 
Family L— AOIPENSEEOIDS. 
depressed at the root of the caudal, which is not the 
(Plate 14, fig. 72 ; Plate 15, figs. 73, 74.) 
case in the members of the more populous genus. 
Acipenser (Sturgeon) nor in that of Planirostra or Poly- 
Tins order containing but one family may be charac- 
odon. Of these forms the family and order consist* 
terized as a single group of Ganoids, whether these be 
The species are numerous in the temperate parts of the 
termed with Agassiz a class of Vertebrals, or with 
northern hemisphere, both in the Old and New Worlds, 
Muller an order of Fishes. The distinctive characters 
but they do not enter the arctic regions, and are 
of the Acipenseroids {Sturiones, Cuvier) are, according 
unknown in the South Seas. 
to Heckel and Kner, an elongated body, protected and 
Among the ancients, says Plinjq the Acipenser was 
made more or less pentagonal by five rows of bony 
considered to be the noblest of fishes ; but it had ceased 
shields; a protractile, toothless mouth on the ventral 
to be esteemed in his time, at which he expresses his 
asjiect ; a blowing-hole and a single operculated gill- 
surprise, since it was rare. The Attilus of the Po, 
opening on each side, but no branchiostegals in the 
which is considered b}^ modern ichthyologists to be of 
membrane ; a cartilaginous internal skeleton ; a hetero- 
the same genus, is stated by Pliny to be sluggish and 
cereal caudal, densely bordered with short bony rays in 
* Dinectes and Proceros are two genera of this family, named 
the upper lobe ; and a long spiral valve in the great 
but not sufficiently characterized by Rafluesque-Smaltz. 
