Until recently there were only two known species of the genus Tribolonotus, apeculiar genus thought to be restricted to New Guinea, but two more were found in the Solomon Islands by members of the Whitney South Sea Expedition and described by C. E. Burt during the year 1930. The following description is of a fifth species, also from the Solomon Group, and I have named it for the Rev. Father J. B. Poncelet, who has collected many excellent specimens of many kinds for the Trustees of the Australian Museum. Owing to the general shape of the body and the rows of large spines or scutes on the dorsal surface of this lizard, it has been referred to by laymen as a young crocodile. The native name, supplied by Fr. Poncelet, is Ubaibo.