 Over the years, he continued his exploration of the fossil trees, eventually unearthing the oldest known reptile in the history of life, which he named "Hylonomus lyelli" in honour of his mentor.From 1855 to 1893 he was professor of geology and principal of McGill University in Montreal, an institution which under his influence attained a high reputation.In 1859 he published a seminal paper describing the first fossil plant found in rocks of Devonian origin.