ICHTHYOLOGY. 559 



generic, and specific names when they are mentioned. &quot;Which is the most 

 numerous family? Which is the smallest? Which most useful for food? 



NOTE. 



M tiller s classification of fishes (made in 1846) is the most recent, but it 

 has since been somewhat modified. This gives eleven orders, viz: 1. DER- 

 MOPTERI, in which he includes the Amphioxidas or Lancelots, placed in the 

 sub-order Pharyngobranchii ; and the Myxinoidei, (Myxines, ) and Petro- 

 myzontidae, (Stone-Suckers,) in the sub-order Marsipobranchii ; II. MAL- 

 ACOPTERI, with sub-orders Apodes, Abdominales ; III. Pharyngognathi, 

 with sub-orders Malacopterygii, (including Scornberesocidaa, and Acanthop- 

 terygii, (including Chromidae, Cyclo-Labridae, Cteno-Labridae ;) IV. ANACAN- 

 ITHINI, with sub-orders Apodes, (including Ophididas,) and Thoracici, (in 

 cluding Gadidae, Pleuronectidae, and Echineida? ;) V. ACANTHOPTERI ; VI. 

 PLECTOGNATHI ; VII. LOPHOBRANCHII ; VIII. GANOIDEI ; IX. PROTOPTERI, 

 which includes the one family Sirenoidei, made up of Lepidosiren paradoxa, 

 of Brazil, and Lepidosirtn or Protopterus annectens, of the Gambia River, 

 Africa; X. HOLOCEPHALI, (including Chimasroidei and Edaphontidre;) XI. 

 Plagiostomi. 



Agassiz, in the &quot;Essay on Classification,&quot; contained in his recently pub 

 lished work, thus remarks, - I am satisfied that the differences which exist 

 between the Selachians, (the Skates, Sharks and Chimaeraa,) are of the same 

 kind as those which distinguish the Amphibians from the Reptiles proper, 

 and justify their separation, as a class, from the Fishes proper. I consider 

 also the Cyclostomes as a distinct class, for similar reasons ; but I am still 

 doubtful whether the Ganoids should be separated also from the ordinary 

 Fishes. This, however, cannot be decided until their embryological devel 

 opment has been thoroughly investigated, though I have already collected 

 data which favor this view of the case. Should this expectation be realized, 

 the branch of Vertebrata would contain the following classes : 



1st class: Myzontes; with two orders, Myxinoids and Cyclostomes. 



2d class: Fishes proper; with two orders, Ctenoids and Cycloids. 



3d class : Ganoids ; with three orders, Coelacanths, Acipenseroids and 

 Sauroids; and doubtful, the Siluroids, Plectognaths and Lophobranches. 



4th class: Selachians; with three orders, Chimaaraa, Galeodes andBatides. 



5th class: Amphibians; with three orders, Caecilise, Ichthyodi and Anura. 



6th class : Reptiles ; with four orders, Serpentes, Saurii, Rhizodontes and 

 Testudinata. 



7th class: Birds; with four orders, Natatores, Grallae, Rasores, Insessores, 

 (including Scansores and Accipitres.) 



8th class: Mammalia; with three orders Marsupialia, Herbivora and 

 Carnivora.&quot; 



