The Beluga Whale has the species name Delphinapterus leucas (D. leucas). The Latin name of this whale can be interpreted in the following way:
Delphin = dolphin
A = without
Pterus = horn (at least in this case, though it can also mean wing)
Leucas = white

So, in short, “the white dolphin without a horn”.

Here are some more facts about the Beluga Whale:
Size of population: 50 000-70 000
Distribution: Around the North Pole
Status of species: Vulnerable (according to IUCN)
Length of male (bull): 4,2-5,5 m
Length of female (cow): 3-4,1 m
Weight of bull: 1-1,6 tonne
Weight of cow: 400-600 kg
Sexual maturity of bulls: 8 years
Sexual maturity of cows: 5 years
Life expectancy: 30-40 years

Source: Beluga.is

Read about how divers bond with Belugas under the pack ice in the December 2010 issue of Popular Mechanics - on sale on 22 November.