Some Sort. Whether the Particles Which Remove the Charge Come from The

some sort. Whether the particles which sloths. A second series, composed of Olzy- remove the charge come from the air, or chodectes and Conoryctes, is clearly an allied from the condensed gaseous layer, or from group, which probably gave origin to the the material of the body itself, is still in Armadillos. dispute. It appears to me that the mass These two series I have arranged under a of the evidence is in favor of the latter new suborder for which I have proposed hypothesis. But the possibility that the the name Ganodonta, and considered them phenomena may be complicated by elec- as constituting a primitive division of the trolytic conduction in the medium sur- Edentata. rounding the charged body,* must not be This suborder has been defined as fol- forgotten. lows : ('Primitive Edentates characterized ERNESTMERRITT. in the earlier forms by rooted teeth with CORNELLUNIVERSITY. divided fangs, having a more or less com- (To be conoluded.) plete enamel investment ;in the later forms by the teeth becoming hypsodont, rootless, of persistent growth, and by limitation of THE MRTH AXERICAAT ORIGIX OF THE EDENTAT3S.t tlie eaaniel covering to vertical bands in THE explorations of the American Mu- progressive decrease. By the presence of seum Paleontological party in the basin of incisors in both jaws, by a typical molar and the San Juan, New Mexico, during the past premolar dentition, by a trituberculate summer secured, among other important molar crown, which disappeared early in materials, the larger part of the anterior life through wear, leaving the dentine ex- limb of Wittacotherizun multi,fragunz Cope, as- posed." sociated with the lower jaws and a number The evidence of the Edentato affinities of tlie upper teeth. The specimen in ques- of these forms is displayed most strikingly tion was found by the writer, and, with the in the Hemiganus, Psittacotheriuna, Ectoganus exception of a few unimportant weathered and Stylinodon series in the following char- fragments, was bedded in its original matrix, acters : (1) The enlarged teeth in the front a soft, friable, reddish colored clay. The of both upper and lower jaws can now be jaws and limb wore not more than a foot determined as being canines, and not in- apart, so that there can be very little doubt cisors, as has formerly been supposed. In that they belong to one and the same indi- the earliest genus, Henziganus, from the lower vidual. Puerco, the lower canine had already lost It has been the custom of paleontologists the enamel from its posterior face, while the to place the genus Psittacotherium, after Cope, crown of the upper canine is completely in the Tillodontia, but it can now be shown encased in enamel ; the teeth were rooted, that it not only does not belong in this having divided fangs, and the crowns of the group, but that together with IIemiganus, molars arid premolars in the single speci- Ecfoganus and Xtylinodolz forms a closely con- men known are enamel-covered. (2) In nected consecutive series ancestral to and the succeeding genus, Psittacotherizcm, from leading directly to the Gravigrada, or ground the upper Puerco, the superior canines had also lost the enamel from the posterior *In an early paper Arrhenius [W. A. 32, 545; face, the roots of the lower molars and pre- 33, 638. Phil. Mag. 28, p. '751 suggested that the molars were connate, while the roots of the air conducted electrolytically under the influence of ultra-violet rays. upper molars mere more or less divided into t Bull. Amer. Mus. Nat. Hist., Art. XVI., 1896. fangs. The crowns of the molars early lost 866 SCIENCE. [N. S. VOL. IV. NO. 102. their tuberculate structure and all the We know of no other group of extinct molars and premolars are more or less mammalia in which this progressive loss of elongated ; the incisors were reduced to a enamel occurs, coupled with increasing single pair in the lomrer, and very probably length of the teeth, together with their a like number in the upper jaw, with the growth from persistent pulps ; and when we enamel confined to the anterior face. (3) come to consider the remarkable similarities In the Wasatch representative (Ectoganus) in other parts of the slzeleton, the conclu- a still further advance is seen in that the sion, in my judgment, is unmistakable that canines grew from persistent pulps; the they are the direct forerunners of the Eden- lower incisors had lost their enamel cover- tata. It is, indeed, a matter of great surprise ing, and in the premolars the enamel is con- that the foot structure of Psittacotherium, and fined to external and internal vertical bands. for that matter Hemiganus as well, should (4) The Wind River and Bridger genus show, even at the very beginning of the (Stylinodon) continues this specialization, Puerco, such a high degree of specializa- and here we note that in the premolars, and tion, almost equal to the large Ground molars as well, the enamel is confined to Sloths. It clearly indicates that the modern narrow external and internal vertical bands, Edentates are the surviving members of a with all the teeth hypsodont and growing very ancient and archaic group of mam- from persistent pulps. (5) The feet of all malia, which had its origin far back in these genera, so far as known, are remarka- Mesozoic time. bly short and provided with immense more It is also a matter of the greatest interest or less compressed claws. (6) The car- to note that this group apparently disappear- pus and ulna and radius of Psittacotherium ed from North America before the close of are almost identical with that of Mylodon, the Eocene, no trace of them having as yet and the humerus of Ectoganus displays a re- been found later than the Lower Bridger markable similarity to that of lllylodon and horizon, until they reappear in the Pliocene Megalonyx. (7) The muzzle is short, the or Post-Pliocene beds of this country. It lower jaw is heavy and robust, and the pos- is also worthy of note that they make their terior end of the tooth line passes behind first appearance in South America in the the enlarged coronoid, which, together with Santa Cruz and Monte Kermoso formations, tho large, powerful curved canines, grow- which would seem to indicate that these ing from persistent pulps, at once recalls, beds cannot be older than late Eocene or in the most positive manner, the skull of older Miocene, corresponding with our Megalonyx. (8) The order Edentata, with Uinta and White River formations. Col- the exception of one or two fossil forms, lateral evidence of this migration to the from the Banta Crux and Monte Hermoso southward in Eocene time is furnished by beds of South America, are characterized the disappearance of Meniscotheriz~mfrom by enamelless teeth, growing from persist- our Wasatch and the subsequent appear- ent pulps, notwithstanding the fact, as has ance of its successors, the Proterothe~iida:in been shown, that they possess a rudimen- South America. tary enamel organ for each tooth in the I think, from the evidence just adduced, earlier stages of its development. Ameg- that it can now be established that the hino has found that some of the older South American Edentata, at least, origin- forms possessed bands of enamel on the ated on the North American continent in molars and premolars similar to those seen the group above described. in Stylinodon. J. L. WORTMAN. .

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