232 ZOOLOGY. 
what the bill of a parrot. The teeth are compound, composed of numerous 
laminz, which are constantly being renewed as they are worn away. In 
Diodon there is but one such compound tooth, occupying the whole of 
each jaw: the skin is armed with slender prickles, or stout spines. Several 
species are known in the United States, the most abundant of which is D. 
maculo-striatus, or the balloon-fish. D. punctatus (pl. 81, fig. 19) is a 
common species of tropical waters. In Tetraodon the single tooth appears 
to be divided in each jaw by a deep incision, producing four pieces in the 
mouth. The body is not cased in an inflexible coat, as Diodon, and the 
dermal appendages are less highly developed. Some species of the genus 
will inflate themselves to a great extent by swallowing air and causing it to 
pass into a sac immediately beneath the skin: irritating them will cause 
them to exhibit this property. When thus inflated they become much 
lighter than the water, and float about on the surface. The spines with 
which the body is provided then stand up erect, and furnish a secure guard 
to the animal. These same remarks apply, in a less degree, to Diodon. 
One species of Tetraodon is electrical, T. electricus. Pl. 81, fig. 20, repre- 
sents T. lagocephalus. Four species are known in American waters. 
- The remaining genus Orthagoriscus is composed of fishes whieh appear 
to have had the tail abruptly cut off. The jaws are undivided, as in 
Diodon, but the skin is not capable of inflation. The high dorsal and anal 
are united to the caudal. The largest species, Orthagoriscus mola, known 
as the sunfish, or head-fish, is occasionally caught off the coast of the 
United States. It is a fish of large size, weighing sometimes as much as 
400 lbs. 
The order Lophobranchii, characterized by having the gills in small 
tufts instead of being pectiniform, is composed of two families, the Synena- 
THipa and the Hierocampma, both much restricted in their genera and 
species. Considering them most conveniently as one family (as we may 
here), we find three prominent genera, Syngnathus, Hippocampus, and 
Pegasus. The genus Syngnathus embraces fishes with a tubular snout, 
somewhat like that of the Fistularide: the body generally straight and 
elongated, and the ventrals absent. The whole body covered with plates. 
The most curious feature consists in the possession by the male of a false 
pouch under the tail, into which the ova are conveyed by the female, and 
there hatched ; being retained for a considerable time before final expul- 
sion. This is the case in Syngnathus acus (pl. 81, fig. 16). In Syngnathus 
ophidion (pl. 81, fig. 15) the eggs are merely attached beneath the abdo- 
men, and not protected by lateral folds of the skin. One species, S. 
peckianus, or pipe-fish, is known on the coast of the United States. In 
Hippocampus, called the sea-horse, the body is broader and shorter; the 
tail, however, is slender: there are no ventral and caudal fins; and an anal 
only in the females. One species, H. hudsonius, is frequently thrown up 
on the Atlantic beaches of the United States. Pegasus has long, broad 
pectorals, and a mailed body, which is shorter and stouter than that of the 
preceding. The dorsal and anal fins are opposite. The mouth is placed 
at the end.of a.salient snout, but is inferior, not terminal. One of the most 
436 
