204 W. S. MacLeay on the Natural Arrangement of Fishes, 



doubt of its being nearly as follows into genera, or rather into fami- 

 lies ; — 

 VER^, M'Clel. Body regular. 



1. P^ONOMIN^, M'CleL, or genus Cyprinus, L. Intestinal canal 



long ; representing STURIONES. 



2. SARCOBORINiE, M'CleL, or genus Leuciscus, KL Intestinal 



canal short ; representing OSTINOPTERYGII. 

 APALOPTERINjE, M'Clel. Body invested with a slimy mucus. 



3. PCECILIAN^, M'CleL, or genus PfficiLiA, Sch. Snout prolonged, 



no cirri. Branchial rays more than three ; repre- 

 senting LOPHOBRANCHII. 



4. COBITIN^. Mouth provided with cirri. Branchial rays three ; 



CYCLOSTOMI. 



5. PLATYCARIN^, M'CleL, or genus Platycara, M'CleL Head 



flattened, round and short. No cirri, branchial rays 

 less than three; representhig PLAGIOSTOMI. 

 Thus we see why the Platycara has the form of a shark ; why 

 Loaches, such as Schistura, M'CleL, have an analogy to the Lam- 

 preys and Myxines ; why Psilorhynchus has so long a snout ; and 

 why Gonorhjnchus has the muzzle of a sturgeon. The nearer two 

 groups are in general structure, the more striking their parallel ana- 

 logies will be ; and therefore I think, that by comparing fish with 

 fish, we may obtain more striking analogies than by comparing them, 

 as Swainson does, with Mammalia, birds, or insects ; at all events, 

 we shall have less reason to distrust the effects of a fertile imagina- 

 tion. Still I am far from denying, that such analogies as he delights 

 in exist in nature. I only say, that they are dangerous things to deal 

 with, and that in his hands they often become far-fetched and even 

 ludicrous. The cause of the greater part of the resemblances which 

 he discovers between objects the most apart from each other in ge- 

 neral structure, seems to be a general law of nature, which has ruled 

 that in every group of animals there should be a minor group more 

 essentially carnivorous, another minor group more essentially herbi- 

 vorous, another more aquatic or natatorial, and so on. These minor 

 groups may also be characterized by one being more essentially ter- 

 restrial, another more essentially aerial, another more aquatic, an- 

 other more amphibious, and so on. These general principles are the 

 occasion of resemblances between animals the most distinct in their 

 structure, and therefore I understand perfectly what Swainson means 

 when he speaks of a Rasorial type of fish ; yet surely it is an incor- 

 •rect expression, for so far from fishes having been created on the 

 models of Rasores or Grallatbres, for all that we know, birds may 

 have been created on Plagiostomous or Cyclostomous types. The 

 general model was undoubtedly one ; but why Swainson should as- 

 sume this one model to have been taken from birds I cannot divine, 

 except that in ornithology he is most at home. However, to return 

 to the subject of Cyprinidm, your arrangement of them shows another 

 set of analogies, which I also think very conspicuous ; for instance. 



The Pseonominae are the types of the family Cyprinidse. 



The Sarcoborinse represent the Esocidse. 



The Pcecilianse represent the Clupeidae. 



The Cobitinse represent the Salmonidse. 



The Platycarinse represent the Siluridse. 



