ICHTHYOLOGY. 



261 



Classifica- 

 tion — Ma- 

 lacopteri. 



least six laj'ers, readily separable the one from the other, 

 as well as from the subjacent muscles, to which it is attached 

 merely by a loose and scanty cellular tissue. These apo- 

 neurotic layers extend to the caudal. They are thin, dense, 

 and can be stretched under the finger ; their external sur- 

 faces become flocculent when they imbibe water. These 

 flocculi resemble moist cotton, and when examined with a 

 high microscopic power, present a felt-like interlacement of 

 extremely minute fibrils. The tunics receive from their 

 interior sides filaments of the same nerve {par vagum, Ru- 

 dolphi) which runs under the aponeurosis. There are other 

 filaments also of extreme tenuity, which penetrate the six 

 layers to expend themselves on its interior surface ; these 

 spring from the intercostals. In thus deriving the nervous 

 energy of its electric organs from the "vagus" and from the 

 " rami ventrales " of the spinal nerves, as well as in possess- 

 ing the cellular apparatus of the Torpedo and the laminated 

 membranous one of Gi/nmotus, the Malapterurtis com- 

 bines the characters of these two genera in its peculiar organ. 

 In the Edinburgh Philosophical Journal for 1856, Mr 

 Murray gives a good figure of a species of this genus from 

 the Bight of Benin. The Arabs, fully appreciating the na- 

 ture of the bemmibing powers of the Malapterurus, name 

 it Haad or Raasch (thunder). The fish gives its discharge 

 when touched on the head, but is powerless when held by 

 the tail, and in fact the electric organ does not reach the 

 caudal fin. In giving a shock it moves the tail however, 

 as it must do when the muscles of the body are acting. A 

 fish of only seven inches in length can give a vigorous dis- 

 charge. The fish is eaten, and it is one of the most esteemed 

 Siluroids as an article of diet. 



M. Valenciennes considers Trichomycterus and Eremo- 

 philus as forming a link between the Siluroids and the Cy- 

 piinoids, through Cobitis; indeed, he was long in doubt as to 

 which family they actually belonged, and he has been led 

 to assign them a place among the Siluroids chiefly by the 

 absence of subopcrcula. The want of an adipose fin weighed 

 less with him, as this member is wanting also in some Silu- 

 roids; neither does he consider the absence of ventrals of 

 sufficient importance to exclude a genus from a family 

 grou)). Trichomijcteri were found by Mr Pentland in the 

 rivulets which liill into that vast alpine sheet of water, Lake 

 Titicaca, which is frequented by the Cyprinoid Oreslias, 

 also an apodal, and in the affluents of the Apurimac, one of 

 the sources of the Amazon. He discovered them also in 

 Kio de Guatanai, Rio de Pontezualo, and in Lake Compu- 

 cila, on the Andes, to the west of Cuzco, and at an elevation 

 of 14,000 feet. Eremophilus inhabits the waters of the 

 Valley of Bogota, 8oOO feet above the sea level. 



Family XVIII.— SILURIDiE, Agass. 



Skin nalied, or covered with bony shields, without scales. Pre- 

 maxillaries forming the border of the upper jaw, the niaxillaries 

 being reduced to mere vestiges, or elongated into barbels ; all have 

 barbels; suboperculum wanting. Kpicoracoid wanting, or reduced 

 to a mere process of the coracoid. The postfrontal or temporal ap- 

 paratus has two ossicles less than in most osseous fishes ; the pseudo- 

 branchiae are wanting. The swim-bladder is present in the majo- 

 rity, and is connected by a chain of ossicles with the acoustic organ ; 

 no pancreatic ca^ca ; stomach ca;cal. In most the first pectoral ray 

 ifl very strong and serrated; most have an adipose fin upon the 

 back. Branchiostegals nine to eighteen, 



ANALYTICAL TABLE OF THE SILVRIDjE (Dum.) 



Dorsal, single (Siluro'idcs, Dum.) 

 Uor^al, containivg bony rayt. 



Dorsal extending along the whole back, Clarus 33. 



Dorsal short, with 



Its ijjinou} ray close to the skull TraCHF.LOPTEBUS 24. 



Its sjjinous ray on the back. 



Caudal forked ScniLBES 2. 



Caudal rounded Brontes 31. 



Doras 



37. 

 35. 

 40. 



38. 

 36. 



29. 



28. 



6. 



Dorsal sustained by branching rays. 

 Eyes lateral. 



Eyes conspicuous SiLURUS 



£yes scarcely visible Cbtopsis 



Eyes <m the dorsal aspect. 



Tail slender^ tapering, trenchant AsPREDO 



Tail tapering little Saccobkanchus 



Dorsal on the tail, without bony rays Malapterurus 



Dorsals two (Diptcronotes, Dum.) 



Second dorsal witli bony rays united to the caudal. 



Head protected by abony helmet Chaca 



Head clothed with soft skin Plotosus 



Second dorsal with one bony ray, not united to the caudal. 

 Head helmed ; body cuirassed ; barbels. ..Callicuthys 

 Second dorsal destitute of bony rays ,- body naked. 

 tSnout elongated. 



Snout round ; lateral line keeled, ) 



spinous J 



Snout broad, Jlat, arched. 



Eyes lateral, level with the nos- 1 pl^tystoma 



trils J 



Eyes depressed below the nostrils.. .Hypophthalmus 25. 

 Snout short. 



Head covered by a bony helmet. 



Dorsal long ; body very long Heterobranchus 34. 



Dorsal long; body abbreviated SVKODONTIS 27. 



Dorsal short ; barbels Bagrus 4. 



Dorsal short; no barbels Silundia 9. 



Head naked. 



Caudal round at the end PiMELODUS 16. 



Caudal forked. 



Barbels more than four Galeiohthys 7. 



Barbels two only Diplomvstax. 



Barbels none Ageneisoshs 26. 



Obs — Dumeril includes Arius, No. 13 ; Phractocephalus, No. 

 5 ; and Pangasius, No. 8, under the genus Bagrus, No. 4 ; and he 

 omits from his table Astroblepas, No. 32, and Eremophilus, No. 43, 

 together with several other genera characterized by Valenciennes. 

 His genus Diplomystax is founded on Arius papillosus and A. raninus 

 of the Histoire des Foissons ; and he has instituted a genus Conosto- 

 mus for the reception of the Pimelodi that have elongated conical 

 muzzles terminated by a small mouth ; and which have moreover 

 very small adipose fins. Macrones, another of his genera, embraces 

 several BagriviiWi long slender muzzles, and an adipose fin longer 

 than the anal, together with a very long scaleless body. 



Genus I. Silurus, Linn. Dorsal short on the fore part of the 

 back, without sensible spines ; no adipose fin ; a long anal. Uaduli- 

 forni or card-like teeth on the jaws, and a band of vomerine ones 

 behind the premaxillaries. Some have four barbels, and some 

 only two. Sixteen species. 



Genus II. Sciiilbes. A strong, denticulated dorsal spine, ele- 

 vated nape, broad depressed head, greatly compressed body, and 

 very distinct teeth. Barbels eight. Branchiostegals eight to ten. 



Genus III. Cetopsis, Agass. Eyes almost imperceptible, being 

 nearly covered by skin. Six barbels. One dorsal composed of 

 soft rays. Convex, obtuse, truncated head ; moderate mouth ; single 

 row of teeth on the mandible and front of the vomer; a band some- 

 times on the premaxillaries. Gill-opening a small hole; branchio- 

 stegals ten. 



Genus IV. Bagrus, Cuv. and Valenc. (Mystus, Artedi.) A 

 rayed dorsal with spine, and an adipose one; a pectoral spine. A 

 band of villiform or card-like teeth on the premaxillaries, behind 

 which, on the roof of the mouth, there is a second arched villiform 

 band, or a single row of teeth, not separated in the middle. They are 

 divided into groups according to the number of their barbels, and 

 subdivided by the forms of the head, the lengths of the adipose or 

 anal, and variations in their dentition. Sixty-one species are de- 

 scribed in the Jlistoire des Foissons. In Bagrus Jilamentosus the air- 

 bladder is divided by a septum, in which there is no opening; and 

 in other species, the lateral compartments are subdivided by trans- 

 verse septa. 



Genus V. Phractocephalus, Agass, (SiVaj-aci, Spix,) Incom- 

 plete osseous rays, encased in the upaer border of the adipose fin. 

 A flat head, with a deeply sculptured rony casque ; and an expanded 

 transversely oval shield before the dorsal, free, and altogether de- 

 tached from the bones of the skull. Nine branchiostegals; six 

 barbels round the mouth. 



Genos VI. Platystoma, Agass. {Sorubim, Spix.) Snout de- 

 pressed, Branchiostegals numerous. A transverse band of teeth, 

 but more completely divided by the smooth median line of the 

 vomer into two plates on each side, than in the Bagri. Thirteen 

 species. 



Genus \'II, Galeichthys, Valenc, Head rounded, skinny, 



Classifica- 

 tion — Ma- 

 lacopteri. 



