88 DIODONTID.E. 



further from the true fislies by the conceahnent of the opercles, and 

 the branchial rays and gills, by the integuments ; and from the Sharks, 

 to which, in the imperfection of the jaws and ribs, and in the softness 

 of the bones, they indicate an approximation, by the single branchial 

 cleft, and general structure, which is that, with the above exceptions, 

 of the true fishes ; the bones, though soft, yet being in their structure 

 truly fibrous. Internally they have no ctEca, but in general a large air- 

 bladder ; and externally the order is marked further by the want of re- 

 gular or ordinary scales, and ventral fins. By this last character they 

 may be instantly distinguished from the Acanthopterygian Lop h idee ; to 

 which, at various points, they seem at first sight closely linked. That 

 this relation is, however, one of parallelism or analogy rather than of 

 affinity, I am convinced with Cuvier ; in opposition to the opinion of 

 my late friend, Mr. Bennett,* and the stream of former systematic- 

 writers. Though the voracity, the capability of inflation, the softened 

 skeleton, the small branchial slit, the concealment of the gills and 

 opercles, the button-shaped nasal pedicle, the pedicellate fins, the form 

 of body, and the skin-armour of certain Plectognathi, find their antitype 

 in some or other of the Lophida ; yet the general structure of these last, the 

 distinct formation of the palatal arches and the jaws in all, and the nature 

 and position of the teeth in some, together with the impossibility of se- 

 parating the more anomalous Cheironectes from the less doubtful Lophius, 

 using these epithets in allusion to their natural affinities, — all these con- 

 siderations show sufficiently that the general bias of the Lophidte is away 

 from the Chondropterygian series of fishes, whilst that of the Plectognathi 

 is towards it ; and that the degree and kind of their relation finds its 

 correct expression by the arrangement of each at qorresponding points of 

 two parallel series, rather than by placing both consecutively in one. 



The two families which compose this order Plectognathi are easily 

 distinguished from each other by the structure of their teeth and skin. 

 The former in the Balistida are few in number, but distinct and of the 

 ordinary sort ; and the skin is divided into hard bony or rough compart- 

 ments, rather than scales. The teeth in the Diodontida are united into 

 one or two large bony masses in each jaw ; and the skin, though generally 

 armed more or less with spines, is itself even, soft, and naked. 



The fishes which compose this latter family are all remarkable for their 

 oddness of form and general grotesqueness of appearance. The Sun-fishes 

 (^Orthagoriscus) resemble rather mutilated halves of some deep sort of 

 fish than perfect animals : and the Diodons and Tetrodons or Globe- 

 fishes remind one in their prickly armour of the Porcupine and Hedgehog ; 

 or, when inflated, take the form of a balloon or globe. In reference to this 

 peculiarity. Dr. Roget, in the first volume of the fifth Bridgewater Trea- 



* See Zool. Joiirn. iii. 372, 373. 



