FAMILY SCINCIDAE (SKINKS).
The largest family of lizards in the world, skinks are found in all parts of Australia. About 350 species are currently recognized as occurring within Australia. The typical skink is a smooth scaled lizard which has well developed legs and is diurnal.
However many skinks don't fit the pattern just described. Some have spiky scales, others lack legs or have reduced limbs, whilst others are nocturnal.
Reproductive habits range from egg laying (Oviparous), to live bearing (Ovoviviparous and Viviparous), depending on species.
The only positive ways to distinguish a skink is by the head scales which are usually symmetrical and large, and the presence of a large broad fleshy tongue. Within Australia no other lizards are similar to skinks. They range in size from 5 cm to 60 cm.

The above was from the book Australian Reptiles and Frogs by Raymond Hoser and now available on a fantastic CD-Rom along with a vast amount of other information, papers and the like on reptiles, frogs and other wildlife.