SIWALIK HILLS, a mountain range which runs parallel with the Himalayan system, from Hardwar on the Ganges to the banks of the Beas (Bias). It belongs to the tertiary deposits of the Outer Himalayas ; and it is chiefly composed of low sandstone and conglomerate hills, the solidi fied and upheaved detritus of the great range on its north. Its northern slope leads gently down into the Debra Doon, a vale between the Hima laya and their outlying Siwalik subordinates.
thick forest of sal.and sain clothes the lower sides, while on the higher crests pine woods indi cate a cooler climate. Wild elephants abound ; and the fauna in this section also includes tigers, iloth-bears., leopards, hymnas, spotted deer, pigs, and monkeys. The total length of the range from the Ganges to the Beas is about 200 miles, and its average breadth about 10 miles. All the great rivers which run at right angles to the Siwaliks —the Ganges, Junina, Sutlej, and 13eas—have worn themselves valleys through this chain. The Siwalik Hills are about 8 to 10 miles across, and are a mass of boulder and sandstone hills, generally quite dry, but broken up into ravines, through which sudden floods or raos 'rush in the rains. The Siwalik Hills, which bound the Doon to the south, are in height from 400 to 600 feet.
It is in these hills that extensive fossil remains were discovered by Dr. Falconer and Captain Cautley. Of the quadruniana or monkey tribe may be mentioned species of the Palmopithecus, Semnopithecus, and Macacus. One of the carni vora, the great sabre-toothed tiger, Machairodus latidens, DOW quite extinct, is remarkable for the enormous development of its canine teeth, and also for its wide distiibution. It has been found in Kent's Cavern, Torquay, in the Norfolk forest beds, in the miocene tertiary deposits of Epples beim in Germany, the Auvergne in France, the Val d'Arno in Italy, the pampas deposits and bone caves of South America, and the upper miocene fresh-water limestones of the Siwalik Hills.
These hills also contain remains of extinct species of the Proboscidea or elephants, various species of Mastodon have lived there, and also in Burma, and also in Armenia, many parts of Europe, and N. and S. America. Dr. Falconer described 13 species of fossil elephants, 9 of which are from India. Amongst these are Elephas ganesa, with tusks 10i feet long, and it MILS probably the largest of all the extinct elephants.
One of the ungulata or hoofed animals of the Siwalik, the three-toed miocene ancestor of the horse (the Hipparion or Hippotherium), occurs fossil, and has also been found at Pikermi in Greece, and in France and Germany. Remains of
the hippopotannis have als.o been found in the newer rniocene deposits of the Siwalik.
India has also furnished fossil remains of two pigs, the Sus hysudricus and Sus giganteus.
The newer tertiary deposits of the Siwalik also furnished remains of the Sivatherium, a gigantic four-horned ruminant, bearing some resemblance to the living antelope of India. Fossil remains of the camel have also been found there ; and, of three extinct species of the ruminant Chalico therium, one is from India, and one from China, while in the later tertiaries of the Siwalik have been found the heads and horn cores of fossil oxen and antelopes.
In the newer miocene deposits of the Siwalik also have been found the bones of a fossil ostrich, Struthio Asiaticus, and the remains of a huge crane, Argala Falcoueri.
The tertiary rocks of India have also furnished retnains of alligators, crocodiles, and gavials. Some of the existing tortoises are large, but the extinct Colossochelys atlas, discovered by Dr. Falconer in the Siwaliks, exceeds in size all known chelouian remains. From the pieces found, the shell of one has been restored in the British Museum, and it measures 20 feet iu longitudinal, and 15 feet in lateral girth.
Mr. W. T. Blanford is of opinion that the fauna of the Siwalik Hills belongs to the pliocene formation. In Sind, strata containing miocene marine fossils pass up into beds with a mammalian fauna, including some of the older Siwalik forms, such as 'Mastodon, Chalicotherium, Dorcatherium, etc., together with Dinotheriurn, Hyopotanius, Ilyotheriuni, Anthracotherium, etc., which have never been found iu the true Siwaliks. These Sind beds are apparently equivalent to the Lower Siwaliks, which are nufossiliferous in the typical area. In the Middle and Upper Siwaliks, instead of the old forms just named, elephas, loxodon, ccrvine, and bovine ruminants in abundance, and other recent types, are found. As the Sind beds cannot be older tha,n upper miocene, the typical Siwaliks must be pliocene. The mammal Bos (l3ubalus) palminclicus, found in the Upper Silva liks, occurs also in the Nerbathla alluvium, asso ciated with palmolithic implements.—Nature, 5th September 1878 ; British Museum Catalogue ; Falconer's Palivozoie Ilemains ; Beng. and Roy. As. Soc. Journ. ; Gaz.