148 



SCIENCE. 



similar size, a point of much interest, in view of what 

 has been noted by Prof. Marsh with regard to the brains 

 of extinct Mammals : finally, both forms had well- 

 developed teeth in both jaws, but those of Hesperornis 

 were implanted in a continuous groove, while those of | 

 Ichthyomis had separate sockets. 



Prof. Marsh calls attention to the peculiar combin- 

 ation, in Ichthyomis, of a low feature — the biconcav- 

 ity of the vertebrae — with a comparatively high method 

 of implantation of the teeth, and adds : " Better ex- 

 amples than these could hardly be found to illustrate 

 one fact brought out by modern science, that an ani- 

 mal may attain great development in one set of char- 

 acters, and at the same time retain other low features 

 of the ancestral type. This is a fundamental principle 

 of Evolution." 



Naturally, the teeth are described and figured with 

 especial fullness and accuracy. Their general feat- 

 ures are distinctly reptilian, as would have been in- 

 ferred. Curiously enough, in neither genus does the 

 dental series reach the tip of either jaw, and, in Hes- 

 perornis, "the extremity of the premaxillary bone, 

 back to the nasal openings, has its surface pitted with 

 irregular vascular foramina, indicating, apparently, 

 that it was once covered with a horny bill, as in mod- 

 ern birds." P. 8. 



With the exception of Archaopteryx, all the known 

 odontornithic remains are in the Museum of Yale 

 College, but their discoverer is clearly of opinion that 

 more are to be found : 



" These three ancient birds, so widely different 

 from each other, and from all modern birds, prove 

 beyond question the marvellous diversity of the avian 

 type in mesozoic time, and also give promise of a rich 

 reward to the explorer who successfully works out the 

 life-history of allied forms, recorded in ages more re- 

 mote." P. 189. 



He even ventures to define the leading features of 

 the, at present, hypothetical progenitor of the entire 

 group of birds : "In the generalized form to whicii 

 we must look back for the ancestral type of the class 

 of birds, we should therefore expect to find the follow- 

 ing characters : Teeth in grooves ; vertebra bicon- 

 cave ; metacarpal and carpal bones free ; sternum 

 without a keel ; sacrum composed of two vertebrae '■ j 

 bones of the pelvis separate ; tail longer than the 

 body ; metatarsal and tarsal bones free ; four or more 

 toes, directed forward; feathers rudimentary or im- 

 perfect; quadrate bone free." P. 188. 



As compared with this generalized form, our mod- 1 

 ern birds, while endowed with intense functional ac- ! 

 tivity, and in some structural features — especially as I 

 to their true dermal appendages — a most highly spec- ! 

 ialized group, are nevertheless, odontologically con- 

 sidered, degenerated and retrograded creatures. 



The general bearing of the facts given in this 

 memoir upon the question of evolution has been well 

 stated by Prof. Marsh upon a previous occasion. 



" Compsognathus and Archceopteryx of the Old 

 World, and Ichthyomis and J/esperornis of the New, 

 are the stepping-stones by which the evolutionist of 

 to-day leads the doubting brother across the shallow 

 remnant of the gulf, once thought to be impassable." 



So far we have had to deal either with facts, or with j 

 hypotheses based upon those facts and warranted by 

 the prevailing opinions respecting evolution in gen- I 



eral. There remains to be considered the bearing of 

 these same facts upon the zoological relations of the 

 toothed birds to the rest of the class. Here there is 

 room for very wide disagreement, and the only point, 

 perhaps, upon which all seem to be in accord, is that 

 the Birds, as a whole, form a class of vertebrates, 

 whether or not they should be combined with the rep- 

 tiles as a super-class or sub-branch — Sauropsida. 



The advantages of employing a single technical 

 term like odontornithes in place of aves dentatce or 

 toothed birds will be generally conceded, and the use 

 of the term as a convenient designation of certain 

 forms need not imply more than is implied by the 

 words swimmer, flier, apoda, etc. The real question 

 is, do the toothed birds constitute a natural subdivis- 

 ion of the class Aves, comparable for instance with 

 the Marsupials among the mammalia ? If not do they 

 constitute an order or a family, or, finally, are they — 

 or some of them — simply representatives of two or 

 more natural groups, differing from the other members 

 of those groups, and associated together, by the pos- 

 session of teeth ? 



In a natural classification, we expect to find ani- 

 mals collocated either because they agree in many 

 particulars, or because they have in common one or, 

 more features of primary importance For example 

 notwithstanding their immense variety in size, form, 

 habit, existing birds present a remarkable uniformity 

 of structure, even in some apparently insignificant 

 details. On the other hand, although Amphioxus 

 differs from all other Vertebrates in so many respects 

 that nearly all generalizations as to the branch must 

 be accompanied by a qualification, yet it shares with 

 the rest a developmental feature and a general 

 arrangement of organs which keep it within the branch 

 and separate it from all other animals, excepting 

 perhaps the Ascidians. 



Prof. Marsh regards Archceopteryx, Hesperornis, 

 and Ichthyomis, as the representatives of as many 

 orders of the subclass Odontornithes, to which he 

 applies the names Saururce, Odontolcae, and Odonto- 

 tormae. The first of these names had been employed 

 already by Haeckel and Huxley, who, however, had 

 made the Saururas, Ratitae(ostrich, etc.) and Carinatag, 

 (all other birds) subclasses of the class Aves. Marsh 

 does not say what he thinks should be done with the 

 Ratitae, but if he is correct in his opinion (p. 3.) that 

 "Hesperornis and Ichthyomis differed more from each 

 other than do any two recent birds," it would seem 

 to follow that the Ratitae can no longer constitute a 

 subclass of the recent and toothless birds. 



In the condensed statement of the characters of the 

 orders (p. 187) it is shown that we are unacquainted 

 with the mode of implantation of the teeth of 

 Archceopteryx, with the form of its vertebrae and 

 sternum, and with the extent of union of the mandibu- 

 lar rami. The characters enumerated are the pres- 

 ence of teeth, small wings, separate mctacarpaha and 

 a bony tail longer than the body. 



It will be seen that, excepting the teeth, any gen- 

 eralization respecting the Odontornithes as a whole, 

 must be accompanied by a qualification respecting 

 one or two of the orders. Prof. Marsh points out 

 that the three groups present unequal degrees of affin- 

 ity. But even if we exclude Archceopteryx, the only 

 characters which are at the same time common to the 



