12 



Order PLECTOGNA THI Cuv. 



In this order the internal skeleton is less perfectly developed than in 

 the Teleocephali. The exterior is covered with ganoid plates, granu- 

 lations or spines. The supramaxillary and intermaxillary bones are 

 united together into a continuous piece. The branchiae are pectinated ; 

 the branchial apertures small. The air-bladder has no duct. 



In this order the Diodontoids and Tetraodontoids, popularly called 

 " Puffers," " Blowers" and " Balloon fishes," and the Balistoids or " Trig- 

 ger fishes," are included. 



Order LOPHOBRANCHTI Cuv. (Kaup.)* 



The internal skeleton is less perfectly developed than in the Pectini- 

 branchiata. The external skeleton is composed of polygonal plates, of an 

 osseous and corneous structure, and which are joined to each other, but 

 permit considerable mobility in the animal. The jaws are produced into 

 an elongated tubular mouth. The branchiae are tufted; the branchial 

 apertures small and on each side of the nape. The air-bladder has no 

 duct communicating with the intestinal canal. 



This order embraces representatives of only two genera on our coasts, 

 the well known " Pipe-fishes" and <: Sea-horses," or the Si/ngnatlu and 

 Hippocampi of naturalists. In the tropical, and especially the Asiatic 

 seas, the order is represented by quite a large number of genera and 

 species, which have been distributed by modern systematists among three 

 decidedly distinct families. 



Subclass GANOIDEI (Agassiz) Miiller. 



The subclass of the Ganoidei or Ganoids, as revised by Miiller, embraces 

 forms in which the vertebral column and skull are either osseous or car- 

 tilaginous. The scapular arch is directly suspended from the skull. The 

 exo-skeleton is generally deposited in the form of ganoid plates, but there 

 are, in representatives of some families, oval or cycloid scales, and the 

 body is still more rarely naked, and the bony plates absent. The optic 

 nerves, like those of the Plagiostoms, are only connected by commissure 

 and do not decussate. The bulbus arteriosus is muscular, and provided 

 with two or more rows of valves, which in one order are replaced by two 

 spiral and longitudinal valvular folds. The intestine has frequently, but 

 not always, a spiral valve. There are no special intromittent organs. 

 The branchial apertures are simple fissures or spiracles on each- side, as 

 in ordinary fishes ; the branchiae are free. An air-bladder is present, and 

 communicates by a duct with the intestinal canal. The ventrals are 

 abdominal. 



*"Catalogue of Lophobranchiate Pish in the collection of the British Mu- 

 seum. By J. J. Kaup, Ph. D. &c." London 1856. 



Article " Ichthyology" by Sir John Richardson, in the recent edition of the 

 " Encyclopaedia Britannica." 



