In talking about the races of the galaxy it wouldn't be right to mention some of the races that didn't make it.
The first we will discuss is The Feathertron. These were a beautiful sea creature that resembled an Earth sea cucumber, the top of which was covered with long feathery projections. Though the individual Feathertrons had only limited intelligence, they were colony creatures, that had the ability to join their nervous systems and cause their individual brains to work as a collective. In this way, they were able to develop mega intelligences.
They developed a written language consisting of five holes scraped in a rock. If a pebble was placed in the holes in certain patterns, it stood for a letter in their alphabet. With this system they could produce twenty-four characters which was more than enough to express their thoughts dramatically.
They left great volumes of science, philosophy, and many works of fiction.  It is not known exactly what happened to The Feathertron's world. The archeological evidence seems to show that suddenly it virtually froze solid! When The Squiggle found it, it was just again beginning to sustain primitive life forms.
The last entry made in The Feathertrons' books was almost virtually the same; 'The Great One has taken away the light. All grows cold. We are dying.'
We can only speculate what blocked the light from their sun. But whatever it was destroyed a great civilization.
The second race we will mention are The Hillbox. It is not known exactly what these creatures looked like, for though they left extensive written records in three systems, they neglected to leave any physical descriptions of themselves! They attained great technological abilities but from their writings they were a cruel and aggressive species that wiped themselves out in a three way civil war that left their worlds devastated and abandoned. It seemed to have been part of their philosophy to destroy the graves of their enemies so no trace of them has ever been found.
It is a strange legacy for all to be left of a race is their hate-filled literature.
The third race we will mention is The Nowfee. They can only be described as frogs. They developed an extensive civilization and had a great deal of technology. When they discovered their sun, which was in the last stages of its existence, was about to go super nova they had the capability to save some of their race, but for some unexplained reason chose not to do. Instead, they sent out robot ships to orbit the planets of far distant solar systems to hopefully be found by others. Inside these robot ships were libraries of all their writings, samples of their artwork, recordings of their music and images of their cultural differences, which have been enjoyed by many long after this race perished.
The last race we will mention is The Dowmoc. This was a very human appearing race, except their feet retained a paddle shape from their aquatic ancestry. And, their heads were longer and thinner, giving them a pointed appearance.
They achieved a moderate level of technology, just enough to wipe each other out with biological warfare that left their world uninhabitable until The Squiggle sterilized it, and reintroduced flora and fauna.
The Dowmoc left the record of their people imprinted on gold sheets in a vast library, housed in their city that survived the longest. It was fortunate The Squiggle found them, and reported all the information on them. Many other races would have simply melted them down for the gold.
There are several other places that it was known races once existed, but these are the only ones that managed to leave behind some information on themselves.It is estimated there may have been as many as twenty-six other civilizations that once existed. But it is very hard to make an accurate count.