The natural history of fishes, amphibians, & reptiles, or monocardian animals . nerally constant in natural groups, of whichthe Sparince, the true perches, and several others, affordample proofs. The most extraordinary development ofa simply forked tail, yet discovered, is to be found inthe Macropodus venustus (Cuv. pi. 197.):, where thelength of this fin is nearly equal to tha*t of the body :and this is the more remarkable, since, in no other generaof its own circle, is the caudal of this form ; a clearindication that it is the rasorial sub-genus. Sometimes,as in Nomeus and Hoplostethus, the
The natural history of fishes, amphibians, & reptiles, or monocardian animals . nerally constant in natural groups, of whichthe Sparince, the true perches, and several others, affordample proofs. The most extraordinary development ofa simply forked tail, yet discovered, is to be found inthe Macropodus venustus (Cuv. pi. 197.):, where thelength of this fin is nearly equal to tha*t of the body :and this is the more remarkable, since, in no other generaof its own circle, is the caudal of this form ; a clearindication that it is the rasorial sub-genus. Sometimes,as in Nomeus and Hoplostethus, the caudal, althoughdeeply cleft, has the two divisions rounded ; but thisform is very uncommon. — Unequally forked, is when one of the divisions ofthe fin is larger thanthe other: our Englishsand-lance (Ammody-tes) shows this verywell (Jig. 4. a); and itis likewise found in allthe flying fish (6), andthe greatest part of thesharks and caudal fins, how-ever, of these latterfamilies are altogetherpeculiar: the rays areby no means symmetri-cal, so that the upperd 2. 36 CLASSIFICATION OF FISHES. lobe of the tail is not formed, as in ordinary fishes,by rays, but by the terminal vertebrae, round whichthe fin is short; while the other, or lower lobe, oftenirregular, is alone composed of rays. No other fishes,yet discovered, possess this sort of caudal fin, nor isthere any thing analogous to it among the osseous orsemi-cartilaginous orders. Another modification of theforked structure occurs in a very few genera, wherethere are two divisions, or rather sinuosities, in the ter-minal margin, analogous to the double fork seen in oneor two birds of the Caprimidgidce. Finally, this struc-ture blends into the rounded form in such fish as havethe even tail already described, but with the middle raysvery slightly shorter than the outer; so that the marginbecomes widely notched, or sinuated, as seen in severalof the salmon family, and many others. (37-) In some genera the caudal fin
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Keywords: ., bookcentury1800, booksubj, booksubjectfishes, booksubjectreptiles
