232 ZOOLOGY. 



what the bill of a parrot. The teeth are compound, composed of numerous 

 laminas, 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 {pi. 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, Jig. 20, repre- 

 sents T. lagoceplialus. Four species are known in American waters. 



The remaining genus Orthagoriscus is composed of fishes which 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 nmch as 

 400 lbs. 



The order Lophohranchii, characterized by having the gills in small 

 tufts instead of being pectiniform, is composed of two families, the Syngna- 

 THiD^ and the HippocAMPiOiE, 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 Fistularidae : 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 {pi. 81, fg. 16). In Syngnathus 

 ophidion {pi. 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 

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