288 



NATURE 



[December 29, 1910 



directly into the modern Felidae, the canines having re- 

 verted from the almost unique machaerodont specialisation 

 to the normal type of carnivorous mammals. The series 

 Dinictis — Nimravus — Pseudaelurus — Felis are in direct 

 succession, structurally and geologically." 



In the opinion of Dr. Matthew the origin of the cat 

 family cannot be carried back further than the Oligocene 

 sabre-tooth, their supposed derivation through the so- 

 called /Elurotherium — which is based on the milk-dentition 

 of a species of the same group — from the Eocene crcodont 

 Palaeonictis being inadmissible. 



Mr. R. O. Peterson has, however, just described, under 

 the name of Daphacnodon, in the Memoirs of the Carnegie 

 Museum at Pittsburg (vol. iv., No. 5), the skeleton of a 

 dog-like carnivore of the size of a large leopard from the 

 Miocene of Nebraska, which, together with the allied but 

 older Daphaenus, he regards as in a considerable degree 

 intermediate between dogs and cats, although the skull 

 and teeth are essentially dog-like. In many respects 

 Daphacnus, of which the whole skeleton is known, is very 

 cat-like, especially in the long leopard-like tail, which 

 may, however, have been bushy. A cat-like feature is the 

 partially retractile structure of the claws. In concluding 

 his description, Mr. Peterson observes that the model " is 

 instructive, as it furnishes at least a conception of a primi- 

 tive form ancestral to cats and dogs." Whether later 

 discoveries in earlier strata will reveal a community of 

 origin for the two groups remains to be seen. 



Reverting to the first article, Dr. Matthew replies near 

 the end to critics who have doubted his theory that the 

 sabre-tooths attacked by dropping the lower jaw into a 

 nearly vertical position and stabbing with the upper tusks. 

 After supporting the theory by additional anatomical 

 evidence, he remarks that most of the early large ungu- 

 lates were of the " pachyderm " type, which were specially 

 suitable to this method of attack, while they would 

 succumb to the mode practised by lions and tigers. 



" With the rise and dominance of the large light-limbed 

 ruminants and horses some of the early sabre-tooths were 

 correlatively adapted into the modern type of felines, while 

 other sabre-tooths, as the surviving pachyderm phyla be- 

 came larger, thicker skinned, and more {>owerful, became 

 progressively larger, more powerful, and developed heavier 

 weapons to cope with and destro}' them. The final extinc- 

 tion of the machaerodont phylum was probably largely 

 conditioned by the growing scarcity and limited geographic 

 range of the great pachyderms." 



Finally, he protests against the idea that these later 

 sabre-tooths died out as the result of over-specialisation. 



Recent conflicting opinions as to the pose of the sauro- 

 pod dinosaurs are discussed by Dr. Matthew in the 

 September number of the American Naturalist (vol. xliv., 

 P- 547)- That these reptiles walked, instead of crawling, 

 the author considers fully proved, their limb-structure, as 

 was previously pointed out by Dr. Abel, displaying a 

 remarkable parallelism to that of proboscideans. This 

 " rectigrade " type, in which the whole limb is pillar-like, 

 with the foot short, rounded, and heavily padded, and the 

 toes reduced or rudimentary, is correlated with gigantic 

 bodily size, the movements being mainly restricted to the 

 upper joints, and the foot serving chiefly as a cushion to 

 minimise the shock. A structure of this kind will 

 obviously occur only among animals which habitually rest 

 their weight on the limbs alone. 



A limit is, however, soon reached in regard to the 

 weight which even the most powerful limbs are capable of 

 supporting in the case of a purely terrestrial animal, and 

 this limit appears to have been attained among the 

 elephants. But if this be so, we are confronted by the 

 question why the saurof>od dinosaurs, with their less per- 

 fectly formed limbs, vastly exceed the largest elephants in 

 bulk and stature. The answer, in Dr. Matthew's opinion, 

 is that these reptiles were aquatic, and adapted to wading. 

 " A wading animal has the greater part of its weight 

 buoyed up by the water, and might attain a much larger 

 size without transcending its mechanical limitations, just 

 as the whales and some true fishes attain a much larger 

 size than any land animal." 



In 1908 Mr. Lambe described a new genus of crocodile 

 (I^idyosuchus) on the evidence of imperfect remains from 

 the Judith River beds of Alberta, Canada. An unusually 

 well-preserved crocodilian skull from the Ceratops beds of 



NO. 2148, VOL. 85] 



Wyoming, recently acquired by the U.S. National Museum, 

 is referred by Mr. C. W. Gilmore (Proc. U.S. Nat. Mus., 

 vol. xxxviii.), in spite of its later geological horizon, to 

 a second species of the same genus, under the name of 

 L. sternbergii. A second skull of the same species, from 

 the Hell Creek beds of Montana, which came under the 

 author's notice after the original paper was written, is 

 also described and figured. 



Leidyosuchus may now be characterised as a short and 

 relatively broad-skulled crocodile, with the nasals appar- 

 ently not reaching the nares, the posterior nostrils wholly 

 enclosed by the pterygoids (instead of being behind them, 

 as in Crocodilus), the mandibular symphyses short and 

 formed in part by the splenial, the upper teeth more 

 numerous than the lower, the first lower tooth received 

 into a'pit, and the third and fourth — which are about equal 

 in size — into notches in the skull. The vertebrae have the 

 cup in front; and there was armour on the lower as well 

 as on the upper surface of the body. Many of these 

 characters connect the genus with Crocodilus on one 

 hand and Alligator (including Caiman) on the other, 

 although their preponderance is with the first-named genus. 

 There are also indications of affinity with the Tertiary 

 Diplocynodon. The position of the posterior nostrils — 

 intermediate between those of modern and Jurassic croco- 

 diles — is just what might have been expected from the 

 geological horizon of the genus. 



Since its original description by Sir R. Owen in 1873 

 the imperfect skull of the saw-billed bird {Odontopteryx 

 toliapica) from the London Clay of Sheppey, preserved in 

 the British Museum, has remained the sole evidence of its 

 genus and species. When complete the specimen probably 

 measured something like 6 inches in length. The dis- 

 covery is now announced by Mr. B. Spalski, in the second 

 number of the new journal published at Leipzig under the 

 title of Der Geolog, of the skull of a much larger species 

 of the same genus in Tertiary strata in Brazil, the total 

 skull-length being no fewer than 5-? centimetres. The 

 name O. longirostris is proposed for the Brazilian species. 



THE INFLUENCE OF RIVER SYSTEMS IN 

 THE EAST. 



G' 



LOBUS for September i, Bd. xcviii., contains an 

 article of some interest on the subject of the influence 

 of river systems in the East, by Herr Ewald Banse. The 

 author deals with the area between 17° and 36° N. lat. 

 and 17° W. and 74° E. long, (which he terms the Orient), 

 where the average annual rainfall is less than 200 mm. 

 (8 inches) ; this is bordered in the southern Sahara and 

 in the northern part of south-western Asia by a broad 

 zone with an' annual precipitation of 600 mm. (235 inches). 

 In summer this area is the hottest part of the earth's 

 surface. It tends to prevent the intermingling of various 

 flora, fauna, and human races ; the Arabian peoples, the 

 one-humped camel, and the date-palm are mainly con- 

 fined to it. The map accompanying the article shows 

 three main areas, which are drained by no rivers — the 

 Saharan, the Arabo-Syrian, and the Irano-Armenian, the 

 undrained regions amounting to 77 per cent, of the 

 Orient. 



The central regions, with their entire lack of hydro- 

 graphic connection with the ocean, differ essentially from 

 peripheral countries with sea-connection. The formation 

 of level plains is one marked tendency of countries devoid 

 of rivers ; wind, which forms the sole connection with 

 the ocean, plays a very important role there. These flats 

 are to be regarded as phenomena of disease in the earth'< 

 surface, and the fact that three-quarters of the Orient_ i^ 

 devoid of river systems will account for its low population 

 and helps to explain its cultural backwardness. It is the 

 watered areas — 23 per cent, of the whole — which have 

 produced the cultures of the Orient, e.g. the Sumerian 

 within the Anatolian-Kurdic belt. Higher cultures con- 

 centrate where there is flowing water all the year. 



Four regions are passed in review, the Atlas countries, 

 the Sahara region, south-west Asia, and western Asia. 

 For each a table is drawn up giving the total area, pro- 

 portions of permanently river-drained, periodically /iver- 

 drained, and entirelv undrained land, and the density of 

 the population— the last, it may be noted, is in inverse 



