134 LOWER VERTEBRATES. 



a lengtli of four feet, and are very destructive to other fishes. The Distichodontinffi 

 and IchthyoborinoB are found in northern Africa, species of Distichodus being impor- 

 tant as food-fishes in the Nile region. 



The SerrasahnoniniB have the belly serrated, the dorsal rather long, and the gill 

 membranes free from the isthmus. The numerous species abound in the waters of 

 South America, and some of them are very singular in form. They are nearly all 

 small in size, but according to Dr. Gunther, " their voracity, fearlessness, and number 

 render them a perfect pest in many rivers of tropical America. In all, the teeth are 

 strong, short, sharp, sometimes lobed incisors, arranged in one or more series ; by 

 means of them they out off a mouthful of flesh as with a pair of scissors ; and any 

 animal falling into the water where these fishes abound is immediately attacked and 

 cut to pieces in an incredibly short time. They assail persons enteiing the water, 

 inflicting dangerous wounds before the victims are able to make their escape. In 

 some localities it is scarcely possible to catch fishes with the hook and line, as the fish 

 hooked is immediately attacked by the ' caribe ' (as these fishes are called), and torn 

 to pieces before it can be withdrawn from the water. The caribes themselves are 

 rarely hooked, as they snap the hook or cut the line. The smell of blood is said to 

 attract at once thousands of these fishes to a spot." 



Sub-Oedee III. — ISOSPONDYLI. 



The great sub-order of Isospondyli comprises those physostomous Teleocephali 

 which have the anterior vertebrae separate and unmodified, and a prsecoracoid arch 

 developed. The lower pharyngeals ha^■e not the form seen in the CyprinidsB, and 

 there are no auditory ossicles. Many species are provided with the adij)ose dorsal 

 fin. Within the order there are many modifications of sti'ucture. Some of the species 

 are fresh-water fishes ; many others are anadromous, that is marine fishes, ascending 

 rivers to deposit their spawn. Others are permanently marine, and still others are 

 adapted for life in great depths. A very large portion of the Bassalian or deep-sea 

 fish fauna is made up of Isospondyli. Such usually have a very feeble osseous and 

 muscular development, and a very strong dentition. They are also often provided 

 with series of phosphorescent spots. Isospondyli are found in all parts of the world 

 except in the rivers of some portions of South America ^nd Africa. 



About thirty families of Isospondyli are usually recognized. Most of these group 

 themselves naturally about the important families of Clupeidse, Sahnonidas, and Stomia^ 

 tidae ; most of the deep-sea forms being more or less allied to the latter group. 



The family of CHiEOCENTKiDJi: contains but a single species, Chirocentrus dorab, 

 a large fish of the Indian Ocean. 



The Engeaulidid^, or anchovies, are small fishes allied to the herrings, but 

 having the mouth very broad, its gape extending nearly to the gill opening, and 

 overlapped in front by a short snout. About seventy species are known, abounding 

 on the coasts of most temperate and torrid regions, and sometimes ascending the 

 streams. They swim in large schools, and are fishes of weak organization. All are 

 silvery in color, and most of them have a burnished silvery lateral band. They are 

 much used as bait, and some of the species are salted or pickled in large numbers. 

 Most of the species belong to the genus Stolephorits (Etigraulis), and the longest 

 known species is the anchovy of the Mediterranean, S. encrasicholus. 



The DoEOSOMATiD^, or gizzard shads, are shad-like fishes, having the mouth small, 

 inferior, and toothless, overlapped by a blunt snout. The maxillary is very narrow 



