4 DESCRIPTIONS OF PREPARATIONS. 



For the relations held by the cerebrum and cerebellum to each other and to 

 the tentorium, see Turner, Proceedings Royal Society of Edinburgh, March 3, 

 1862. 



For the various arrangements observable in the system of the vena azygos, see 

 Milne-Edwards, Lesons sur la Physiologic, vol. iii. p. 598, ibique ritata. 



For the histology of the Hibernating Gland, see Hirzel and Frey, Z. W. Z. 

 xii. 1862. For that of the Harderian, in Mammals, see Wendt's Monograph, 

 Die Hardersche Druse, 1877; and in Birds, see MacLeod, Bulletin Acad. 

 Royale Sci. Belgique, 1879, pp. 797-810. 



For a figure and account of the ligamentum diaphragmaticum in the foetal state, 

 see Kolliker's Entwickelungsgeschichte, p. 961, Fig. 587, 1879; and Tr. Z. S. 

 vol. v. p. 286, 1863. 



For an account of the perforation of the clitoris by the urethra in the Cape 

 Mole, see Hunterian Catalogue of the Physiological Series contained in the Royal 

 College of Surgeons, vol. iv. p. 2745 ; for a similar arrangement in Talpa and 

 Stenops and Lemur, see loc. rit. 2810, 2811, 2812. 



For the use of the word ' muffle,' see Waterhouse's Nat. Hist. Mammalia, 

 vol. i. p. 50; vol. ii. pp. 7, 8; Sundevall's Linne's Pecora, Germ. Transl. 1848, 

 pp. 41-43. 



2. SKELETON OF COMMON RAT (Mus decumanus). 



THE skeletons of many of the lower Mammalia bear a general resem- 

 blance to those of certain quadrupeds lower in the scale of life in such 

 points as the nearness of the level at which their trunk is carried by their 

 limbs to that of the ground on which they move ; and in the maintenance 

 by the long axis of their head, of much the same direction as that of the 

 long axis of their entire trunk. But they invariably present the following 

 distinctive characters, which are as peculiar to the Mammalian class as any 

 of the points furnished by the soft parts, such as the blood-cells, the hairy 

 integument, or the mammary glands. In every Mammalian skeleton each 

 half of the lower jaw is made up of a single mandibular bone on each side, 

 which at birth at least, if not, as it is here, throughout life, is distinct from 

 its fellow of the opposite side, and articulates by a convex facet with the 

 squamosal element of the cranial wall ; and the vertebrae in the trunk 

 always differ from those of the different lower Vertebrata in one or more 

 or all of the following points : either in the anchylosis of their several 

 elements, or in the size of their neural canal, or in the shape of the articular 

 ends of their centra, or in the means whereby in the recent state these 

 articular ends are brought into relation with each other. In the vertebra 

 of a young mammal the neural arch may not have anchylosed with its 

 centrum ; but in all such cases two discoid epiphyses belonging to the 

 articular ends of the centrum would also remain unanchylosed, as they fuse 



