Sollas's research was over a wide area; during his lifetime he published over 180 papers and three books, and as well as his geological and zoological studies became an expert in anthropology. His first area of interest was the Cambridge Greensand, which he began working on when studying at the University of Cambridge. He published nine papers on the formation, mainly on the sponges, and for his work was awarded the Wollaston Medal in 1878. From 1878 until 1889 he dedicated his research work entirely to sponges and fossils, publishing a series of papers and reports on new species. In 1887 he wrote an article on phylum for the Encyclopædia Britannica. His work on sponges led him to investigate their physical structure, and from there the makeup of chalk.