SKELETON OF RODENTIA. 365 



skeleton of Dasyprocta Acuchy, showing D 13, L 7, has the supple- 

 mental lumbar vertebra mth sacral characters and connection on 

 the left side : Cuvier assigns to the Dormice (Loirs and Lerots) 

 D 13, L 7 : the burrowing Cape Mole-Rats have twenty or twenty- 

 one dorso-lumbars : in these I have found i3-7, i4-6, and 14-7, 

 and the latter is the number of dorsal and lumbar vertebrae 

 respectively : the Australian Water-Rat {Hydromys chrysogaster) 

 has D 14, L 7 : the best-marked exception is that of the Capromys, 

 which has D 16, L 7 = 23. In some Rodents only one, in most 

 but two, vertebra3 join the ilia : three and four are common 

 numbers of anchylosed sacrals. In the seemingly tailless Cavies 

 and Pacas the caudal vertebra? may be but seven, eight, or ten 

 in number : in the Black Rat and Hapalotis alhipes I have 

 counted as many as thirty. The Great Jerboa has twenty-nine 

 caudals, which also have the proportions and perfections of those 

 in the Kangaroo. 



The met- and an-apophyses commence by a common tubercle at 

 the fore part of the dorsal series ; the anapophysis, fig. 231, D, a, 

 begins to be distinct at the back part of the series, and the meta- 

 pophysis, ib. m, to project from above the anterior zygapophysis, 

 z : both processes are usually well 23 1 



developed in the posterior dorsal 

 and lumbar vertebra?, ib. L : the 

 diapophysis, d, subsides in the 

 posterior dorsals and is lengthened ^"T|j C^ d^ 



in the lumbars, L, by a coalesced ^ , ^ , *^ 



■> ^ J ^ Dorsal Lumbar 



Y\h\Q,t {^pleur apophysis), '^h. d. In vertebra, Lagotis. 



the Great Jerboa (^Helamys) the diapophysis is unusually long and 

 strong in the first dorsal: the anapophysis first projects from 

 the back part of the eighth dorsal, and the metapophysis from the 

 fore part of the ninth : both processes are long in the first five 

 lumbars. The neural spines progressively increase in length to 

 the last lumbar, and are strongly inclined forward toward that of 

 the eleventh dorsal, fig. 232, d : the antecedent spines incline 

 backward to the same vertebra, the spine of which is vertical, 

 and indicates the centre of motion of the trunk. This arrani^e- 

 ment of the neural spines is well marked in all the agile flexible- 

 bodied Rodents. In the Hare, fig. 229, the neural spine of the 

 ninth vertebra, D, indicates the centre. The anapophyses begin 

 on the eighth, the metapophyses on the nintli, dorsal : these in- 

 crease and are continued throughout the lumbar region, where 

 they are very long. The anapophysis assumes the form of a 

 ridge in the last dorsal and lumbar vertebrae. The lumbar 



