264 On the Classification of Animals 



The three orders of Reptiles — Chelonians, Liicertoidy, and 

 Amphibians — make a parallel series with the three lower classes 

 of Vertebrates ; the Chelonians representing the Birds, to which 

 they approximate in some points, besides being betatypic like 

 them ; the Amphibians representing the Fishes, with a still 

 closer approximation between the two ; while the Lacertoids are 

 the typical Reptiles. The Chelonians might be viewed as hemi- 

 typiG Reptiles ; not liypotypic like the Amphibians, but hypertypic^ 

 like the Selachians and Ganoids among Fishes. 



(3.) Fishes are all degradational species in their relations to 

 the animal-type. The two higher groups, or those of Selachians 

 and Ganoids, as already explained (p. 96), are liypertypic. The 

 third, including Teliosts, is typical if viewed with reference to 

 the Fish-type. Below these, the Dermopters or Myzonts (in- 

 cluding Amphioxus, Myxine, &c.), constitute an inferior hypotypic 

 or degradational group, — that is degradational in its relations to 

 typical Fishes (p. 94). Thus typical Fishes are gammatypic in 

 their relations to other Vertebrates, while the alphatypic and 

 betatypic groups are hypertypic orders. 



The following table exhibits the relations of the orders in the 

 classes of Birds, Reptiles, and Fishes ; and, for comparison, those 

 of Mammals are added : — 





Mammals. 



Birds. 



Reptiles. 



Fishes. 



Alphatypic, 



Man. 







Salachiaus, 



Betatypic, 



Megasthenes. 



f Altrices, or 

 \ Pterosthenics. 



Chelonians. 



Ganoids. 



Gammatypic, 



Microsttenes. 



1 Prsecoces, or 

 1 Podosthenics. 



Lacertoids. 



Teliosts. 



Hemitypic or 

 Degradational, 



1 Ootocoids, 



Erpetoids. 



Amphibians. 



Dermopters 



We pass now to Articulates. 



5. Subdivisions of the classes Insecteans, Crustaceans^ and 

 Worms into Orders. — (1.) The higher subdivisions in each of the 

 classes, Insecteans and Crustaceans^ are three in number, none 

 existing above the betatypic grade, which is that of Articulates 

 among the subkingdoms, and of Insecteans among Articulates. 



(2.) Worms are of four types of structure. First, Annelids, 

 or typical Worms, including the Branchiates, Abranchiates, and 

 Nematoids — the last the degradational group, and showing this 

 in the obsolete body-articulations and some internal characters. — 

 Second, Bdelloids or Molluscoid Worms, including the Hirudines 

 or Leeches, Planarians and Trematodes ; characterised by obso- 

 lescent or obsolete body-articulations, and by often wanting the 

 nervous ganglia, excepting the anterior ; by usually a Gastero- 

 pod-like breadth and aspect, an amplificate feature ; by being in 



