554 MR. T. GOODEY ON THE SKELETAL [Mar. 15, 



and for this reason my account will be somewhat full. For 

 purposes of description I have divided the column into four 

 regions, 1, 2, 3, and 4, which are quite arbitrary, and, though not 

 corresponding exactly with any recognized divisions of the body, 

 yet may roughly be described as cephalic, trunk, main caudal and 

 terminal caudal regions. My reason for doing so is, that to 

 treat of the whole length of the column in a continuous descrip- 

 tion would mean a needless repetition of words, thus tending to 

 make the meaning obscure. The regions are as follows : — 

 1. Anterior cephalic portion extending for about twelve centi- 

 metres behind the skull. 2. The region extending from the 

 posterior end of 1, over the abdomen a,nd reaching to the level 

 of the cloaca; what may conveniently be termed the "trunk 

 region." 3. The main caudal region extending from the posterior 

 end of 2 to a point about eleven centimetres from the tip of the 

 tail. 4. The last eleven centimetres of the tail, terminal caudal 

 region. 



h. Description of Regions 1, 2, 3, and 4. 



The vertebral column is fused to the cranium quite firmly, so 

 that but slight articulation is possible between the two. In this 

 particular region of the column, viz. 1, there are regular vertebral 

 constrictions of the notochord in the form of ring-like thickenings 

 of the chordal sheath (fig. 9). This figure represents a view of a 

 median, vertical, longitudinal section. It can be easily made out 

 from this that each constriction occurs beneath a basidorsal, and 

 also that the majority of the constrictions are well calcified. 

 This particular point is of considerable interest, and is here fully 

 dealt with. The first five constrictions — counting from the left — 

 are calcified regularly, so that each centrum is typically cyclo- 

 spondylic, being in the form of a short cylinder pinched in round 

 the middle. The calcined areas thus present the appearance of 

 two Y's placed point to point. The sixth centrum has a calcified 

 V above, but below, the calcification is irregular, being repre- 

 sented by only a small patch of calcareous secretion. The seventh 

 is regular above, but below, the "V is calcified all over. Eight, 

 nine, and ten are also regular above and below, except that the 

 lower V is larger in each case than the upper one, the latter in 

 the tenth being very small. Constrictions are visible beneath 

 basidorsals eleven, twelve, and thirteen, but no calcified areas are 

 apparent in these cases, although, externally, the notochord shows 

 definite calcified bands in the case of eleven and twelve. With 

 these two, then, it is evident that calcification has not proceeded 

 as far inward as in the more anterior ones. It also reveals the 

 fact that the process of the deposition of calcareous salts begins 

 on the outside of each constriction, and gradually proceeds 

 towards the interior. Constrictions ele\'en and twelve may be 

 looked upon, therefore, as being in a state of semi-calcification, 

 whilst thirteen is merely a constriction of the chordal sheath, in 

 which calcification has not commenced. The intervertebral 



