MOKPH(>L<»(U('AL METHOD AND RECENT PROGRESS IN ZOOLOGY. 585 



di,sc(n'eiy of the 'ritiniotliciiu. tlic Aiul)lyopod:i, tho Dinoceratu, with 

 their .stnuioe diiiiimitive brain, cliiei" amono-the heavier imgiilato forms, 

 is to consider the Manuualia anew; and when it is found that among 

 late discoveries we have (1) that of a series of Rhinoceratoidea, which, 

 though not yet known to extend so far hack in time as the primitive 

 tapirs and horses, are complete as far as they go; (2) that among the 

 Ruminants we have, in the Oreodontida^ of the American Eocene, 

 primitive forms with a dentition of 44 teeth, an absence of diastemata, 

 a pentadactyle manus, a tetradact>de pes with traces of a hallux, and, 

 as would appear from an example of ^Lxoreodon^ a bony clavicle, such 

 as is unknown in any later ungulate, we are aroused to a pitch of eager 

 enthusiasm as to the outcome of labors !iow in hand; for as I write 

 there reaches me a letter to the effect that for most of the great ver- 

 tebrate groups, and not the mannnals aJonc. collections are still coming- 

 in, each more wonderful than the last. 



In the extension of our knowledge of the Ancylopoda, an order of 

 mannnals named after the AncyJ()therinin. of Pikermi and Samos, which 

 occur in the early Tertiaiy deposits of Europe, Asia, North America, 

 antl alnuidantly in Patagonia, we have been made aware of the exist- 

 ence of genera w^iose salient structural features combine the dentition 

 of an ungulate with the possession of pointed claws, believed to have 

 ))een retractile, like those of the living cats. Conversely to these 

 unguiculate herbivores, which include genera with limbs on both the 

 artio- and perisso-dactyle lines, there have been found among the 

 so-called Mesonychida? undoubted primitive carnivores, indications of 

 a type of terminal phalanx seal like and approximately nonunguiculate; 

 from all of which it is clear that we have in the rocks the remains 

 of forms extinct which transpose the correlations of tooth and claw 

 deducible from the living orders alone. Further among the primitive 

 pentadactyle Carnivora we meet, in the genus Pat riof ills, with a 

 reduction of the lower incisors to tw^o, and characters of the fore limb 

 which, with this, suggest the seals. It is, however, prol)able that 

 these characters are in no way indicative of direct genetic relationship 

 betw(^en the two, for inasmuch as tliese animals were accustomed to 

 seek their food in the water of the lake by which they dwelt, their seal- 

 like characters may be ])ut the expression of adaptation to a partially 

 aquatic modc^ of life of parallelism of moditication with the seals, and 

 nothing more. 



Early in the history of their in(]uiry our American confreres recorded 

 from the Pliocene lh(> discov(My of camel-like forms possessed of a full 

 upper incisor dentition — for exampl(\ the genera Protohihix and Ithi/- 

 graiDitiodon — and now they have ari'i\(Hl at the conclusion that while 

 the camels ai'c of American origin one of their most characteristic 

 ruminants, the Prongbuck {A)ifU()aipv(t)^ would con\'ersely appear to 

 l)e the descendant of an ancestor {Blusfoniery,!) that migrated fi'om the 

 Old World. 



