The genus is associated with one long extinct in Europe.
The horns, usually present in both sexes, are small and straight, situated far back on the forehead; and between them rises the crest-like tuft of hair from which the genus takes its scientific name.
By early writers the word was generally given as an equivalent of the Linnaean Loxia, but that genus has been found to include many forms not now placed in the same family.
The genus Pyrophorus contains about ninety species, and is entirely confined to America and the West Indies, ranging from the southern United States to Argentina and Chile.
It is the principal genus of the natural order of Monocotyledous Potamogetonaceae, and contains plants with slender branched stems, and submerged and translucent, or floating and opaque,.
Amphitherium, of the Stonesfield Slate, typifies the family Amphitheriidae, which includes the American Dryolestes, and in which some would class the European Purbeck genus Amblotherium, although Professor H.
Robur, one of the most valued of the genus, and the most celebrated in history and myth, may be taken as a type of the oaks with sinuated leaves.
On the principle of contradiction this division is both exhaustive and exclusive; there can be no overlapping, and no members of the original genus or the lower groups are omitted.
In common with the okapi, giraffes have skin-covered horns on the head, but in these animals, which form the genus Giraffa, these appendages are present in both sexes; and there is often an unpaired one in advance of the pair on the forehead.
These long-chinned mastodons are now regarded as forming a genus by themselves (Tetrabelodon), well-known examples of this group being Tetrabelodon angustidens from the Miocene and T.
The name of the genus is derived from Arauco, the name of the district in southern Chile where the trees were first discovered.
There also occurs a peculiar genus of lizards with two species, the one marine, the other terrestrial.
The only species of this genus is about the size of a small rat, found in the interior of Australia.
Of the Old World forms, the family Triconodontidae is typified by the genus Triconodon, from the English Purbeck, in which the cheek-teeth carry three cutting cusps arranged longitudinally.
The tree in this instance is one of the acacias, a genus distributed through all parts of the continent.
There are genera so far removed from every living genus that many connecting links must have become extinct.
The British oak is one of the largest trees of the genus, though old specimens are often more remarkable for the great size of the trunk and main boughs than for very lofty growth.
The plant generally understood by this name is Nepenthes, a genus containing nearly sixty species, natives of tropical Asia, north Australia and (one only) of Madagascar.
The live oak is one of the most valuable timber trees of the genus, the wood being extremely durable, both exposed to air and under water; heavy and closegrained, it is perhaps the best of the American oaks for shipbuilding, and is invaluable for water-wheels and mill-work.