REPTILES. 



other circnmftances in their orpranization and habits, befides 

 the polleflion of branchix and lungs, have been adduced as 

 arguments. Others have contended that they arc perfe6t 

 animals ; and the more exadl refearehes ot modem natu- 

 ralifls and anatomills fecm to have linally proved thai this is 

 the cafe. The anatomical details, by which this conelufion 

 is iupported, will be found towards the end of the article. 



As the firen and protcus, truly, perfeft animals, have 

 been fometimcs conlidered as larvx or imperfedl ftatcs of 

 unknown reptiles, fo the contrary error has been committed, 

 of defcribing the larvx of known fpecies as perfeft animals 

 allied to the fireu and proteus. Laurenti, one of the firft 

 naturahlls who endeavoured to reduce the clafs of reptiles to 

 regular order, ellabliflied a genus (protcus) for Uich batra- 

 cian reptiles as, according to him, poflcH'ed both branchi-^r 

 and lungs. To this genus he has afligncd the tadpole of 

 the rana paradoxa, under the name of proteus raninus ; 

 and another, which he himfelf infpected, and which has 

 finee- been afcertained to be the larva of an aquatic falaman- 

 der, under that of proteus tritonius. (See his Specimen 

 medicum exhibens fynopfin rcptilium.) The firen operculata 

 of M. de Beauvois (Tranfaftions of the Philofophical So- 

 ciety of Philadelphia, vol. iv. ) is confidered by Cuvier as a 

 fimilar initance, and perhaps as the very axolotl or Mexican 

 animal, which will be deicribed prefently. He regards, in 

 the fame light, an animal defcribed by the very learned 

 writer on amphibia, Mr. Schneider, as found in the lake 

 Champlain : fee Hift. Amphib. Nat. et Litter. Fafcic. i. 

 p. 50. He fays it may be objefted that we cannot eafily 

 conceive that fo complicated an apparatus as that of the 

 branchije, their cartilaginous arches, and the mufcles moving 

 thein, fhould difappear and leave no trace behind ; but, as 

 the larva; of our falamanders experience fuch a change, the 

 Angularity of the phenomenon cannot be pleaded as an 

 objeftion to it. Recherches, &c. p. 117. 



Anatomy of the Axolotl, or large Mexican Salamandrlne 

 Tadpole. — Another animal of this kind is one found very 

 commonly in the lake furrounding the city of Mexico, and 

 noticed by the early writers in their accounts of thofe coun- 

 tries, and of the interelling objefts they produce, although 

 not methodically defcribed or fcientifically inveftigated until 

 very lately. Hernandez fpeaks of it in two places ; in 

 one, under the name of the eatable tadpole (gyrinus edulis), 

 or atolocatl (Hift. Anim. Miner. Nov. Hifp. lib. unic. 

 Traft. 5. cap. 4. p. 77 : this book is placed at the end of 

 the abridgement by Recchi) ; in the other, under that of 

 lufus aquarum, pifcis ludicrus, or axolotl (ibid. cap. 2. 

 p. 76, and in the large abridgement by Recchi of the whole 

 work of Hernandez, lib. 60. cap. 4. p. 316.) This ac- 

 count, accompanied by a figure of fome other animal, was 

 copied into other works with various errors. 



Dr. Shaw defcribed an individual fent immediately from 

 Mexico to the Britifli Mufeum, and gave two ggod figures 

 of it ; in the Naturaliil's Mifcellany, N° 343, under the 

 name of gyrinus mexicanus ; and in the General Zoology, 

 vol. 3. pt. 2. pag. 612. pi. 140, under that of firen pifci- 

 formis, confidering it as allied to the genus firen. 



Mr. de Humboldt met with it in Mexico, and recognifed 

 it as the axolotl of the Mexicans and firll Spaniards, under 

 which name it is ftill known. He brought fpecimens of it 

 to Europe, and entruited their anatomical invettigation to 

 the experienced hand and profound judgment of Cuvier, 

 whofe defcnption we extraft from the Recherches fur les 

 Reptiles douteux, already quoted, pag. 109. et feq. pi. 12. 



Anatomy of the Axolotl. — In its fize and general configu- 

 ration it very clolely refembles the falamander terreftris 

 (lacerta falamandra) of Europe. No one would hefitate 



in calling it a falamander, were it not for the branchiie, 

 wiiich latter refcmble very narrowly thofe of the larvn; of 

 falamanders, and float loofcly at the fides of the neck. 



The openings communicating with the mouth are four 

 in number, and much larger than in the firen. A fold of 

 the /kin of the head forms a fpecies of operculum for the 

 four. There are four arches, as in filhes, and we fliould 

 hence cxpeft five openings, but the fourth is immediately 

 united to the trunk. The two intermediate arches have, 

 towards the mouth, two rows of pointed denticuli ; but the 

 firft and fourth poflefs, each, only a finglc row. None of 

 thefc denticuli exift towards the operculuin, fo that the firft 

 of the four openings is not denticulated in any diredlion. 

 Each of the four arches has, towards the outfide, a fliarp 

 membranous crifta, which might deceive fuperficial obferva- 

 tion by caufing a refemblancc to the gills of a fifti ; but 

 there is no vafcular nct«work for refpiration, and the arterial 

 trunks follow, without any divifion, the three firit arches 

 to arrive at the branchial tufts, which are the only true 

 gills. There are three of thefe tufts on each fide, attached 

 to the three firft arches, where the (kin joins them together ; 

 the operculum and the fourth arch have none. Thefe tufts 

 are much more ramified than thofe of the firen, but their 

 ramifications refemble a lock of hair, and are not arranged 

 with fo much regularity. 



0/?(o/ojy.— The head is the fame as in the falamanders, 

 except that the cranium is rather broader. The teeth are 

 placed in the fame way on the edges of the jaws ; there are 

 moreover two plates immediately behind the edge of the 

 upper jaw ; byt the two longitudinal feries, which are ob- 

 ferved along the palate of the European falamanders, could 

 not be perceived. The head is articulated in the atlas by 

 two condyles, as in the firen and falainanders. 



The apparatus for fupporting the branchias is very fimi- 

 lar to that.of the firen ; and, at the time of the metamor- 

 phofis, a part of it probably remains to form the os hyoides 

 of the falamander. The middle piece is cylindrical, fhort, 

 and terminated behind by a forked extremity. The front 

 end fupports two cartilages, the ends of which, fufpended 

 to the angles of the jaw, correfpond to the hyoideal branches 

 of fifti : they are immediately under the membranous oper- 

 culum. From the pofterior end of this middle piece pro- 

 ceed two other branches on each fide ; a broad one fupport- 

 ing the firft cartilaginous arch, and a more llender one 

 trifurcated to fupport the three other arches. The four 

 branchial arches are fufpended, by their outer extremities, 

 to the firft vertebra. 



There are feventeen vertebrx from the head to the pelvis ; 

 and twenty-three from the latter to the end of the tail. 

 The fpinous procefles of both are longer than thofe of the 

 falamander ; and they exift on both afpefts of the caudal 

 vertebras, which makes the vertical meafurement of this 

 part exceed that of the European aquatic falamanders. 



There are thirteen fmall ribs on each fide, fimilar to thofe 

 of the falamander. 



The ofteology of the limbs refembles in all refpefts that 

 of the falamander, excepting the more pointed form of the 

 laft phalanges, which has occafioned them to be taken for 

 nails. 



Organs of Senfs. — The eye is fmaller in proportion than 

 in European falamanders ; but not fmaller than that of 

 the fpecies brought from the Alleghany mountains by 

 Michaux. 



Organs of Circulation. — The vena cava receives the ter- 

 mination of the veins of the head ; of the branchiae, and their 

 arches ; of the lungs ; of the fore-feet ; laftly, of the inferior 

 vena cava, which has traverfed the liver, and received, as 

 5 C 2 ufual, 



