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number of die fins is no more proper than that of the teeth for this purpofe ; for this is the fame in many genera, and is fometimes different in the feveral fpecies of the fame genus. The afellus longus of authors is evidently of the fame genus with the reft of the afelli, yet they have all three fins on the back, and this has only two ; and on the belly it has only one, whereas they have two there. The fcomber has feven- teen fins, and the thynnus or tunny has twenty-five, or thereabouts ; yet no one can call thefe two genera of fifties, when they agree in all other particulars. The perca, the lucioperca, and the cernua fluviatilis, are all of the fame genus, and have all the fame internal and external charac- ters ; but that the two firft have two fins each on the back, and the laft has only one. The number of the rays in the fins or fifh, particularly in thofe of the back and anus, are very different even in the feveral fpecies of the fame genus ; Hence they are very ufeful in diftinguiftiing the fpecies, but not at all in the genera. We have very evident examples of this, in the feveral fpecies of pearch, cyprini, and many other fifh.
In regard to the other external parts of fifties, there are none which are found in all the fpinofe fifties, and differ in all the feveral genera, except thofe little bones which are found on each fide in the membrane of the head, which covers the gills. Thefe bones are found in almoft all the fifties that have any bones, tho* in fome kinds the thicknefs of this membrane makes them lefs confpicuous than in others. The number of thefe bones is much more regularly and conftant- ly the fame in the fame genera, than that of the fins, as we may find by many obfervations. The four genera of the fcombri, gadi, percse, and fyngnathi, have the number of the fins very various in the feveral fpecies of each genus ; but in all thefe genera the number of the bones in the membrane that covers the gills, is regularly the fame in every fpecies. All the gadi have regularly feven bones on each fide, and fo on of the reft. All the cyprini have three of thefe bones on each fide : All the cotti have fix on each fide : All the clarise feven : All the clupeae eight : All the efoces fourteen ; and fo of the reft. There arc only two known genera of fifh, that do not agree in all the fpecies in the number of thefe bones ; thefe are the falmons and the coregoni. In the firft of thefe the number of the bones is in the feveral fpecies ten, eleven, or twelve ; and in the feveral fpecies of the other, there are eight, nine, or ten, and fometimes but feven. It is an obfervation, however, worthy the naturalift's confi- deration, that nature has given this difference in the num- ber of thefe bones iri the feveral fpecies only to thofe genera in which all the fpecies have fuch a ftrong external reiem- blance in all parts, that fcarce any thing more than the facies externa, was neceffary for the knowing that they belonged to one another ; for befide that all the falmons and coregoni have a membranous appendage refembling a fin on the hinder part of the back, the feveral fpecies of each genus are fo very remarkably like one another, that it is not eafy to di- ftinguifti them in many cafes.
As to the number of the fins on fifh, there are a vaft num- ber of genera which have all the fame general number, as the cyprini, clupeas, coregoni, ofmeri, falmons, cobitides, efoces, pleuronec.fi, fpari, labri, gobii, and gafteroftei ; all have feven fins radiated with bony ribs : The fame number of feven fins, and thofe of the fame kind, is common alfo to the feveral other genera ; but on the contrary, tho' all the fpecies of the fame genus have conftantly the fame number of bones in the membrane that covers the gills, yet it is very rare that the different genera have the fame number. The pearch, the gadi, the ammodytes, and the fcombri, have indeed all feven on each fide. The cyprini and the gaftero- ftei have each of them three on each fide. The cotti, the pleuronedti, and the mugil, have fix each : Thefe however are genera fo very different in their other characters, and in their facies externa, that there is not the leaft danger of their being confounded one with another.
From this it appears very evidently, that the number of thefe bones in the membrana branchioftega, affords the firft and moft effential of all characters for the diftinction of the genera of the catheturous and ofteopterygious, or bony- fin'd fifties. This however is not fufheient alone, tho' it is a great affiftant in determining the genera ; but in order to bring fifh to their proper genera, it is neceffary firft, that ail of the fame genus fliould have the fame number of bones in the gills ; then, that they lhould have in the genera the fame external form and figure; after this, that they muft have the fame fituation of the fins, provided that the num- ber does not differ, which fometimes will be found to vary in fpecies truly of the fame genus ; but in general it is, and ought to be the fame in all.
The fituation of the teeth alfo fliould be the fame, and this generally holds right in the different genera of fifties, all the fpecies having in each natural genus the fame orders of teeth. After this, the fcales are to be examined, and thefe ought to be of the fame fort, and to have the fame fituation. Thefe are the circumftances neceffary to be enquired into, in re- gard to the eftablifhing juft and natural genera. If all thefe agree in all the fpecies ; and added to this agreement there Suppl. Vol. I. . I
be an analogy in the fituation and form of the other internal and external parts, particularly in the ftomach, and its ap- pendices, in the Inteftines, and in the air-bladder, there will remain no doubt of the genus eftablilhed on fuch foundations being perfectly juft and natural.
It is not to be expected however, that every one of thefe cha- racters fliould be found regularly in every fpecies of the fame genus in the fame perfection ; fome will fhew them more, others lefs, and others will want fomething of them : But the three grand things that are effential to the famenefs of the genus, are the fame number of bones in the bran- chioltege membrane, and the fame general external face or figure, and the fame fituation of the fins. The other cir- cumftances are additional and confirmative. Upon the whole it appears, the number of certain parts is the firft great foundation of generical diftinctions in fifties ; and that no one note or generical character can be fo ex- tenfive as to take in the whole at once, but that other cha- racters lefs effential but more numerous muft be in fome cafes taken in for the eftablifhing the whole feries of Icb- thyologicai diftinctions. Artedi Ichthyolog.
ICHTHYOLOGISTS, authors, who have written concerning fifhes. The authors who have left us treatifes on this fub- ject, are very numerous ; and are ranged by Artedi into their feveral proper dalles, with great care and candor. The fyftematical hhthyoiogijli arc Ariftotle, Pliny, Ifidore, Albertus Magnus, Gaza the interpreter of Ariftotlai Marfchall, Wootton, Bellonius, Rondeletius, Salvian, Gef- ner, Aldrovand, Johnftan, Charlton, Willughby, Ray. The Ichthyologijh who have written of the fifhes only of fome particular places, are thefe : Ovid, of the fifties of the Euxine j Oppian, of thofe of the Adriatic ; Aufonius, of thofe of the Mofelle ; Mangolt, of thofe of the Podamic lake ; Paulus Jovius, of thofe of the Tyrrhene fea ; Bened. Jovius, of thofe of the lakcLarius; Petrus Gillius, of thofe of the Maflilian fea ; Figulus, of thofe of the Mofelle ; Salvian, of thofe of the Tyrrhene fea ; Schwenkfeldt, of thofe of Silefia ; Schonfeldt, of thofe of Hamburgh ; Marg- grave, of the Brafilian fifhes ; Ruyfel, of thole of Amboina ; and Francis Valentine, of thofe of the fame place. Of thefe authors, Ovid, Aufonius, Oppian, and Bencd. Jovius wrote in verfe, the reft in profe.
The Ichthyalogifts who have copied all they have written from the works of other writers, and therefore leaft deferve the name, are the following : Pliny, iElian, Atbseneus, Ifi- dore, the author of the Libri de natura rerum, Albertus Magnus, Joannes Cuba, Marfchall, Gelher in great part, Aldrovand in great part, Johnfton, Charlton, and perhaps fome others.
In regard to method, fome have written of fifhes without any method at all ; fome have treated of them in the alphabetical order of their names, and fome have followed a method more or lefs perfect throughout their works. Thofe Ichthyologijh who have attended to no method at all, are Ovid, ./Elian, Atheneeus, Aufonius, Hildegarde de.Pin- guia, Paulus, and Bened. Jovius, Figulus, Salvian in his hiftory of the Roman fifhes, and Ruyfch. Thofe who have written alphabetically, are Cuba, Marf- chall, Salvian in his Tabula Pifcatoria, Gefner, Schonfeldt, Johnfton.
Among the authors who have ufed fome fort of method, thofe come firft who have treated of fifties, according to the places where they are ufually caught. Of thefe are Oppian, Rondeletius, Aldrovand, Johnfton, and Charlton Thofe who have treated of fifties, according to the general di- vifion of them into cetaceous, fpinofe, and cartilaginous, are Ariftode who was author of the method, Wootton, Wil- lughby, Ray; the laft two authors have added to this the numbering the rays of the fins on the back, which is one ftep toward the Artedian method.
The principal and beft authors in this ftudy, and who have reformed and amended it, are Ariftotle, Bellonius, Rondele- tius, Salvian, Gefner, Willughby and Ray. To thefe are to be added fuch as have defcribed only new or particular fifties, who have merited greatly of the world by the new lights they have thrown in upon this part of natural hiftory. Thefe are Paul Jovius, Petrus Gillius, Schonfeldt, Sibbald, Mar- figli, Hebenftreit, and our countryman Mark Catefby : All the reft, except Pliny, Athenaeus, Aldrovand, and Johnfton, are of no ufe or value. Willughby is allowed by Artedi to be by far the beft author on the fubject ; but the world will now give that character to Artedi himfelf. Artedi de Script. Ichthyol.
ICHTHYOMANTIA, bOmpwIiM, in antiquity, a fpecies of divination by means of the entrails of fifties. Potter, Archseol,, Gnec. 1.2. c. 14. T. 1. p. 319.
ICHTHYPERIA, in natural hiftory, the name given by Pr. Hill to the bony palates of fifhes, which are frequently found foffile at great depths in the earth, and ufually immerfed in the ftrata of ftone ; and in this ftate had been named by Mr. Lhuyd, from their refemblance in fhape to. the pods of lu- pines, and fome of the other leguminous plants, jiliquajira. Many from this name, and this cafual refemblance to the pods of plants, have been mif-led into the believing them 14 C fcffil*,
