In the middle line of the hall is placed a magnificent mounted skin of an African Elephant (_Elephas africanus_), fig. 7, from Rhodesia, standing about 11 feet 4 inches in height. The skull of the same individual is mounted on a stand below. Near by are exhibited three tusks, the largest of which measures 10 feet 2½ inches in length. On the north wall, on either side of the Darwin statue, are mounted two African Elephant heads. [Sidenote: Bays or Alcoves round the Hall.] Most of the bays or alcoves round the hall, five on each side, are (with the exception of the one at the north end of the right side) devoted to the Introductory or Elementary Collection, designed to illustrate the more important points in the structure of certain types of animal and plant life, and the terms used in describing them. This has been called the “Index Museum,” as it was thought at one time that it would form a sort of epitome or index of the general collections in the galleries. It is now mainly restricted to a display of the leading structural features in Vertebrated Animals and in Plants. The space being limited, the number of specimens is necessarily restricted. In examining this collection the visitor should follow each case in the usual order of reading a book, from left to right, and carefully study the printed explanatory labels, to which the specimens are intended to serve as illustrations. [Illustration: FIG. 7.--AFRICAN ELEPHANT (_Elephas africanus_). The skull and tusks seen in the foreground are those of the stuffed specimen, the tusks in which have been modelled from another individual.] The bays on the west side (left-hand on entering the hall) are devoted to the Vertebrata, or Animals possessing a “backbone.” In Nos. I and II are shown the characters of the Mammals, which form the highest modification of this type; the wall-cases of No. I containing specimens of the bony framework (internal skeleton). [Sidenote: Bay I. Skeleton of Mammals.] In the first case (south side of the recess) may be seen a complete skeleton of a good example of the class--a Baboon Monkey, with the bones laid out on a tablet, and their names affixed. Below is a skeleton of the same animal articulated, or with the bones in their natural relation to each other, and also named. By examining these two specimens an idea may be obtained of the general framework of the bodies of animals of this class. In other parts of the case are exhibited various modifications of the skeleton to suit different conditions of life. 1. Man, showing a skeleton adapted for the upright posture. 2. A Bat, or flying Mammal, in which, by the great elongation of the fingers, the fore-limbs are converted into wings (fig. 8), supporting a web of skin stretched between them. 3. A Sloth, in which the tips of both limbs are reduced to mere hooks, by the aid of which the creature hangs back-downwards from the boughs of the trees among which it passes its entire existence.