50 



NATURAL HISTORY. 



fourteen vertebrae, the earlier ones elongated and the last five greatly shortened. The species are 

 grouped into two sections first, those in which the carapace is closed behind the anal fin ; and secondly, 

 those in which the carapace is open behind the anal fin. In some species the carapace has three longi- 

 tudinal ridges, in others there are four, five, or even six ridges. Sometimes there are prominent spines 

 which are conical, and project in front of the orbits, or from the ventral, or dorsal, or lateral ridges. 

 None of these fishes attain a large size, the Ostracion cubicus having a length of fourteen inches, and 

 the Ostracion quadricornis reaching a length of sixteen inches. Ostracion bicaudalis is seventeen 

 inches long, but the Ostracion renardi, from Amboyna, is only about four inches long, and there are 

 many other species of abotit this size. Like the other genera in this family, the Ostracion is most 

 abundant in the Malay Archipelago, the West Indies, and tropical coasts of Africa. Two specimens 

 of the Ostracion quadricornis have been taken near Mervagissey, on the Cornish coast. 



FAMILY II. GYMNODONTES. 



This family, in addition to having a sharp cutting beak without teeth, formed of the bones of the 

 fore part of the head more or less blended together, has the dorsal, anal, and caudal fins soft and 

 approximating towards each other. The ventral fins are absent, but the pectoral fins are present. The 



TETKODON FAHAKA (FLOATING BELLY UPWARD). 



first genus of this family, Triodon, is so named because the upper jaw is divided by a suture in the 

 middle, while the lower jaw is entire, thus giving the aspect of three teeth, which are large, white, 

 and have the appearance of being powerful cutting organs. The eye is large, being about one-fourth 

 the length of the head. The nostril has two distinct openings on each side of the head. The most 

 distinct characteristic of this fish is furnished by the abdomen, which is capable of being dilated 

 into a large sack which hangs below the body. The air, however, does not penetrate into its lower 

 part, and the sack is kept expanded by a very long pelvic bone. This fish is found widely distributed 

 in the Indian Ocean, and reaches a length of twenty-one inches. The skeleton is well ossified and 

 the ribs well developed, and the body is covered with small bony plates which are spiny. 



The second group has Tetrodon for its type, and though called Tetrodontidce only, has both jaws 

 divided in the two genera Xenopterus and Tetrodon, while the remaining six genera resemble Diodon 

 in having no median suture in the jaws. These fishes are popularly known as Globe-fishes, from the 

 well-known circumstance that after filling the body with air they float on the surface of the water 



