CHAP, in.] VERTEBRAE AND RIBS. 105 



and between which the process of Division has been imperfect. 

 With more reason it may be spoken of as one vertebra partly divided 

 into two, but this description also scarcely recognizes the real 

 nature of the phenomenon. 



Further on, in the same specimen, at the 166th vertebra, there 

 is an even more interesting variation. This vertebra is represented 

 in Fig. 10, II. As there seen, it is normal on the left side, bearing 

 one transverse process and one rib, while on the right side there 

 are two complete transverse processes and two ribs. The 185th 

 vertebra is also in exactly the same condition, being double on the 

 right side and single on the left. 



8. Python sebae : a precisely similar case (Brussels Museum, No. 

 87, I. (Jr.), in which the 195th vertebra is single on the right side 

 and double with two ribs on the left, is described by ALBREGHT, P., 

 Bull MILS. Nat. Hist. Belg., 1883, n. p. 21, Plate II. 



9. Python sp. : a precisely similar case of duplicity in the 168th 

 vertebra, on the left side, in a mounted skeleton in the Canib. 

 Univ. Mus. 



It is to be especially noticed that in each of these four cases of 

 lateral duplicity, the degree to which the process of reduplication 

 has gone on is the same. 



10. Pelamis bicolor [ = Hydropkis~\. The 212th vertebra simple 

 on the left side, and double on the right. It bears one rib on the 

 left side and two ribs on the right side. Yale Univ. Mus., No. 763. 

 BAUR, G., Jour, of Morph., iv. 1891, p. 333. 



11. Cimoliasaurus plicatus (a Plesiosaur). " Centrum of a small 

 and malformed cervical vertebra from the Oxford Clay near Oxford. 

 This specimen is immature, and on one side is divided into two 

 portions, each with its distinct costal facet." LYDEKKER, R., Cat. 

 Fossil Rept. and Amph. in Brit. Mus., Pt. II. 1889, p. 238, No. 

 48,001. 



A case somewhat similar to the above is recorded in the Rabbit by BLAND SUTTON, 

 Trans. Path. Soc., XLI., 1890, p. 341. See also certain cases of a somewhat com- 

 parable variation in Man, considered in connexion with the variations of Bilateral 



Series. 



II. Ribs. 



12. Man. Partial division of ribs is more common than that of 

 vertebra?. Five cases are given by STRUTHERS. 1. Fourth rib 

 becoming broadband bifurcated in front. Male, aged 93. From 

 about middle of shaft these ribs gradually increase in length from 

 7 lines to li inch on the left side, 1^ on right. They then fork, 

 the left l;y inch, the right 1 inch from where they join their 

 cartilages. Cartilage of right forks close to rib, enclosing a space 

 which admits little finger ; cartilage of left lost, but the diverging 

 bony divisions, each of good breadth for a rib (6 to 7 lines) enclose 

 an intercostal space 1^ inch long, attaining a breadth of f inch, 

 which was probably continued forwards by the division of the 



