( 95 ) VI. On a new Genus of the Order Rodentia. By Joshua Brookes, Esq., F.R.S. and L.S. Communicated by the Zoological Club of the Linnean Society. Bead June 3rd and nth, 1828. The science of Natural History is of so unbounded an extent, that perhaps I may be allowed, comparativel}'^ speaking, to say, that scarcely a day passes without an opportunity being afforded to zoologists of bringing to light unknown instances of its latent treasures. The animal which I am at present about to describe has been in my possession for several years ; and although there is strong evidence of its being new to science, as far as relates to a know-ledge of its real structure, yet, from a variety of circumstances, I have neglected to avail myself of the means so long afforded me ; and possibly now it may only be in consequence of the approaching dispersion of my collection that a stimulus is given to exertions, which otherwise might have remained dormant. The individual in question, which appears to be unique, was obtained, when recently dead, from Mr. Cross, in whose Viva-rium at Exeter Change it had been seen while living, and espe-cially noticed, both by M. de Blainville and by M. F. Cuvier. Each of these distinguished naturalists has described its general characters and habits ; but, unacquainted with its real struc-ture, they have failed in referring it to its correct situation in Nature. By each of them it has been erroneously placed among the Jerboas, under the name of Dipus maximus. The latter author.