45S 



NA TURE 



\Scpt.^6, 1880 



and of seizing the abundant fishes of the shallow seas in 

 which it lived. Compared with our modern birds, the two 

 features of this ancient form which most forcibly arrest 

 attention are the teeth and the legs. The teeth were 

 covered with smooth enamel, terminating upward in 

 conical pointed crowns and downward in stout fangs, 

 closely resembling those of mosasauroid reptiles. Their 

 mode of growth and replacement have been determined 

 to have taken place in a manner very similar to that in 

 some reptiles, the young tooth forming on the inner side 

 of the fang of the tooth in use, and increasing in size, 

 while a pit for its reception was gradually made by 

 absorption. The old tooth, being progressively undermined, 

 was finally e.xpelled by its successor, the number of teeth 

 thus remaining unchanged. The teeth were implanted in 

 a common alveolar groove, as in IcJitliyosmtrus. In the 

 upper jaw they were confined to the maxillary and entirely 

 absent from the pre-maxillary bone; in the lower jaw they 

 extended from near the anterior extremity of the ramus 

 along the entire upper border of the dcntary bone. Mr. 

 Marsh believes that they were held in position by cartilage 

 which permitted some fore and aft movement, but on the 

 decay of which after death the teeth readily became dis- 

 placed and fell out of the jaw. This is an important fact in 

 its bearing upon the nature of the teeth found on the same 

 slab of Solenhofen limestone with the well-known'.^/r/iff(;- 

 pteryx. These teeth', it will be remembered, were re- 

 ferred by Mr. Evans to the bird itself — a reference fully 

 confirmed by Mr. Marsh, who says that he at once iden- 

 tified the teeth as those of birds and not of fishes, and 

 by the subsequent discovery of other remains of the 

 bird. In Hcspcroriiis rcgalis there appear to have been 

 fourteen functional teeth in the maxillary bone and 

 thirty-three teeth in the corresponding ramus of the 

 lower jaw. The wings are rudimentary or aborted, 

 a remnant of the humenis alone existing. They may 

 have gradually diminished from disuse until, as the 

 power of flight ceased, the legs and feet increased in 

 proportion, and assumed the massive dimensions shown 

 in the specimens, or, as Mr. Marsh suggests, the bird may 

 have been a carnivorous aquatic ostrich, never having 

 possessed the power of flight, but descended from a 

 reptilian ancestry which is strongly recalled by difl'erent 

 portions of the skeleton. Among recent birds, the peculiar 

 legs and feet of Hcspcroriiis find their nearest analogues 

 in the Grebes of the genus Podiccps. They were admir- 

 ably adapted for propulsion in water, but scarcely served 

 for walking on land. Locomotion must have been entirely 

 performed by the posterior limbs — a peculiarity which 

 distinguishes Hcspcroriiis from all other birds recent or 

 fossiL The tail appears to have been composed of twelve 

 vertebra;, unique in their peculiar widely extended trans- 

 verse processes and depressed horizontal ploughshare 

 bone. Broad and flat, somewhat like that of the beaver, 

 it must ha\e been a powerful instrument in steering the 

 bird through the water. 



The second part is devoted to a description of the 

 remains which have been found of birds belonging to a 

 second order of Odontornithes, termed Odontotormcc. 

 Unlike Hcspcroriiis, they seem to have been all of com- 

 paratively small size and to have possessed powerful wings, 

 but \-ery small legs and feet. From that contemporaneous 

 form, ard from all other known birds recent and fossil. 



they are distinguished by certain types of structure which 

 point back to a very lowly ancestry, lower even than the 

 reptile. Their bones, being mostly air-filled, would enable 

 the carcases to float on water until, by decay or the rapa- 

 city of other animals, they were separated and dispersed. 

 Hence skeletons of these flying birds are less entire than 

 those of the massive-boned Hcspcroriiis. Nevertheless 

 the remains of no fewer than seventy-seven different 

 individuals have been disinterred. These are included in 

 two well-marked genera, Icliiliyornis and Apatornis, 

 and were all small birds, reminding us by their strong 

 wings and delicate legs and feet of the Terns, like which 

 they were probably also aquatic in habit. Besides 

 the reptilian skull and teeth, the birds of this second 

 order were marked by the character of their vertebra:, 

 which in their biconcave structure recall those of fishes. 

 This is the more remarkable, as in Hesperornis the 

 \'ertebrag are like those of modern birds. Yet these two 

 utterly dissimilar types were contemporaries, and their 

 remains have been preserved in the same strata. Mr. 

 Marsh points out that the transition between the two 

 vertebral types may be traced even in the skeleton of 

 IcJitliyoriiis itself, where the third cervical vertebra pre- 

 sents a modification in which the ordinary avian saddle- 

 shaped form appears as it were in the act of development 

 from the biconcave ichthyic form. 



In a concluding chapter the author briefly touches upon 

 some of the broader biological questions suggested by the 

 structure of the animals described in the volume. The 

 striking differences between the three orders into which 

 Prof. Marsh divides toothed birds — Arclucopteryx; Hes- 

 perornis, and Ichtiiyoniis— serve to indicate the high 

 antiquity of the class, ani to encourage the search for 

 ornithic remains in the eanier Secondary, if not in the 

 later Palaeozoic, rocks. The peculiar character of each of 

 the orders Prof Marsh believes to have been united in 

 some earlier type, of which no trace has yet been found. 

 This ancestral type may have been almost as much a 

 reptile as a bird. The earliest birds were doubtless 

 closely related to the Dinosaurs and Pterodactyles. 



Of the plates, thirty-four in number, which accompany 

 and adorn the moriograph it is impossible to speak in terms 

 of too great praise. They are strictly and rigidly scientific 

 diagrams, wherein every bone and part of a bone is made 

 to stand out so clearly that it would not be difficult to 

 mould a good model of the skeleton from the plates alone. 

 And yet with this faithfiflness to the chief aim of the 

 illustrations there is combined an artistic finish which has 

 made each plate a kind of finished picture. We heartily 

 congratulate the genial Professor of Pahi^ontology at Yale 

 on the ad\ent of this truly imperial volume. May it be 

 the earnest of many more from the rich store of materials 

 which he ha-s so courageously and enthusiastically gathered 

 among the wilds of the far West ! 



THE THEORY OF DETERMINANTS 

 A Treatise on the Theory of Determinants and their 

 Applications in Analysis and Geometry. By Robert 

 Forsyth Scott, M.A. (Cambridge : At the University 

 Press.) 



THE list of English text-books on the subject of De- 

 terminants is comparatively meagre, and this not- 

 withstanding the fact that the first separate treatise of all 



