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Show 66 ZOOLOGY OF THE VOYAGE OF TilE DEAGLE. 1 f its borders. I t I.S f·1o m this resemb•l ance7 1~~t'"o .a, O'roove or channel along eac 1 o . l k 'ts specific appellatiOn (.i.r:Leg . ~ortion of a fluted column, that the amma ta es I • laquealns). . . ular elli sis widest at the anterior por- " The crown would resemble an meg p Jnd· ed with enamel, the . . 1 ·11 r of bone surrol tion. The tooth consrsts of a centt·a p• a . b. colour: the transverse . l 1 tt . of a ferrugmous rown . former of a dead white, t le a ei • . l 1 '1st that of Me,T"'. Je.ffer- 1 · d 1 tl n Its lengtl, w ll < 0 . diameter is more than two-t Hr s ess m . d' tet· t's one-half its length m . 1 r t ostenor lame sonii is only one-thud less-t 1e.'tn ero-p . Th roportions of tltis tooth are tlle l'oi·mer and two-thirds less m the latter. e p .1 .1 . s , [VI. de PI cons1'e quent' ly totally at variance wi. th t lm t o f I't s kinureu specie . . XII. fig. 7, 8, 9.]* . f th fore-foot, a radius, humerus, Dr. Harlan descnbes also two claws o e . b. f, mur and ··b an os calcis a metacarpal bone, cet·tam verte Ire, a e . ' scapula, one u ' ' . f h keleton, together with the tooth, tibia, of the same Megalonyx; these p.mts o t e s : . relationship of the species which so fortunately served to estabhsh the genenc . 1 . B'g bone-cave with the iJ'Iegalonyx of Jeff·e rson an d c uv·te l·, were tltscovere( m 1 - ' Tenessee, United States. . . . ic characters of Dr. Harlan does not enter into the questwn of the gener. 11Keualonyx but it would seem that he felt them to rest uot entuely ond d 1 cntal m .< o · ' · · f t1 tooth an <.neemodificatious, for he observes that "a minute exammatwn ° le . I' .. joint re11ders it not improbable, supposing the last named char.actcr to be p~c~1 hl.l to it, that if the whole frame should hereafter be discovered, It may even c auu a generic distinction, in which case, either Aulaxodon, ot· PLE.UHODON, would not be an inappropriate name."t . . .. There can be no doubt, as it appears to me, wtth respect to a foss~l .JUW presenting teeth in the same number, and of the sa~e general structure, as m t~e Megallteriurn, and with individual modifications of form, as well marke? as those which distinguish Megat!terizmt from Jlfegalony.x, that the Palreontolog1st ~as. no other choice than to refer it, either as Fischer has done with Megalonyx, to a d1st~nct species of the genus llfegatlterium, or to regard it as the type of a subgenus distmct from both. With reference, however, to the Pleu1·odon of Dr. Harlan, after a detailed comparison of the cast of the tooth on which that genus is ma.inly ~~u.nded, with the descriptions and figures of the tooth of the Megalonyx Jqfersonn, m the "Ossemcus Fossiles," they seem to differ in so slight a degree as to warrant only a specific distinction, and this difference even, viewing the various ~roportio?s of the teeth in the same jaw of the Megatltm·iurn, is more sati::;factonly established by the characters pointed out by Dr. Harlan in the form and propot·tions of th radius, than by those in the tooth itself. • Medical and Physical Researches, pp. 323-4. t Loc cit. p. 330. FOSSIL M'AMMALIA. The next notice of the Megalonyx which I have consulted, in the hope of meeting with additional and more precise information as to its real generic characters, is an account given by the learned Professor Docllinger, *of some fossil bones, collected by the accomplished travellers Spix and Martius in the cave of Lassa Grande, near the Arrayal de Torracigos, in B1·azil. In this collection, however·, it unfortunately happens that there are no teeth, but only a few bones of the extremities, including some ungueal phalanges, whiclt Professor Doellinger concludes, from their shape, the presence of an osseous sheath for the claw, and the form of their articulation, to belong, without doubt, to an animal of the Megathe1·ioid kind, about the size of an Ox. He particularly states that they are not bones of an immature individual; but that they agree sufficiently with Cuvier's descriptions and figures of the Megalonyx to be reierred to that species of animal (zu dieses thierart ;) and he adds, what is certainly an interesting fact, that the fossils in question form the first of the kind that had been discovered out of North America. Subsequently to the discovery of these bones, and of those of the Mega/onyx laqueatus above alluded to, the remains of another great Edentate animal were found in North America, and were deposited in the Lycenm at New York; among these is a portion of the lower jaw with the whole dental series of one side. It is thus described by Dr. Harlan. "The fragment I am now about to describe is a portion of the dexter lower jaw of the Megalonyx, containing fonr molar teeth; three of the crowns of these teeth are perfect, that of the anterior one is imperfect. These teeth differ considembly from each other in shape, and increase in size from the front, the fourth and posteriot· tooth being double the size of the first, and more compressed laterally; it is also vertically concave on its external aspect, and vertically convex on its internal aspect; the interior or mesial surface is strongly fluted, and it has a deep lo.ngitudinal furrow on the dermal aspect, in which respect it differ·s from the tooth of the M. laqueatus previously descl'ibed by me, of which the dermal aspect is uniform, but to which, in all other respects, it has a close resemblance. I suppose it therefore probable, that this last may have belonged to the upper jaw. The three anterior molars differ in shape and markings: they are vertically grooved, or fluted, on their interior and posterior aspects, a transverse section presenting an irregular cube. 'l'he length of the crown of the posterior molar is two inches : the breadth about five-tenths of an inch: the length of the tooth is three inches and six-tenths. The diameter of the penultimate molar is eight-tenths by seven-tenths of an inch. The length of this fragment of the jaw-bone is eight inches and four-tenths; the height three inches and six-tenths: the length of the space occupied by the alveolar sockets five inches and eight- • Spix and llfartius, Reise in Brazil, Band ii. p. 5. |
