The new Small-Mammal House, erected and occupied in 1905, is a very different structure from the temporary building which formerly occupied the site. The present building is a twin of the Ostrich House, and in it much effort has been expended in devising ways and means to keep its living inhabitants clean, odorless and in good health. Owing, however, to the musky odors secreted by many of the civet cats and members of the Marten Family, it is beyond human power to keep a large collection such as this building contains without a certain amount of wild-animal odor. Most difficult of all collections to settle satisfactorily in a modern zoological park or garden is the great _omnium gatherum_ of small species—and some large ones, also—which fall within the meaning of the term “small mammals.” The number of mammalian miscellanea which can not have buildings all their own is really very great. In addition to that there are always with us a considerable number of young and tender animals which require small quarters, and close attention. The visitor will therefore always find in the Small-Mammal House a great array of viverrine animals, of tropical squirrels and other small rodents, of mustelines, the nasuas, the small marsupials, young leopards, the lynxes and their relatives, baby bears, and many other species. Attention is invited to the great variety of cages in and around this building, of which there are five different types. The total number is 176. All those on the western side are adjustable as to their bottoms and sides, so that it is easy to throw several cages into one, and make cages either very long or very high. The idea of the collapsible cage, and also the general plan of it, has been copied from the model developed and in use in the Zoological Garden of Frankfort, Germany, by Director A. Seitz, to whom this acknowledgment is justly due. It will be noticed that every animal in this building enjoys the use of an outdoor cage, which connects directly with its interior quarters. Of such an odd mixture of animals as we are now to consider, anything like a perfect systematic zoological arrangement is a practical impossibility; but as far as it is possible, we will take up the animals by groups. On the whole, the most striking animals in the Small-Mammal House are the small cats and lynxes. Of the spotted cats, the Serval, (_Felis serval_), of Africa, is one of the rarest. Its long, slender legs, small head, slender body and round spots proclaim it a near relative of the cheetah.