1886.] SaUALORAJA POLYSPONDVLA. 535 



Vertebral Column. — In the subject of fig. 1 the vertebral column 

 is beautifully shown beyond the shoulder-girdle, though somewhat 

 imperfect in front. As already described by previous writers, the 

 vertebrae (fig. 8) are merely slender, concentrically marked rings, of 

 the truly " tectospondylic "^ type, and in the sfiace just mentioned 

 no less than 340 can be counted ; in the abdominal region, sixteen 

 of these occupy the length of a centimetre, while in the tail the 

 proportions are so slightly different that only one more ring is com- 

 prised within the same distance. The obscure portion in front of 

 the pectoral girdle measures one and a half centimetres in length, 

 probably representing about 24 vertebrae ; and if three centimetres 

 are missing from the end of the tail ^, this loss will indicate an 

 additional 48. The total number is thus found to be approximately 

 400, as estimated by Davies in the large specimen described in 1872. 



In the more aged individuals (e. g., no. II.) the vertebral rings 

 are more robust than those of the apparently yonng {e.g., no. III.) ; 

 and it is remarkable that in no example is there any trace of the 

 fusion of the elements in the region of the neck. 



But it is not necessary to add a detailed account of the structure 

 of the vertebrae themselves, for they have already been carefully 

 examined and described by no less an authority than Professor Carl 

 Hasse, of Breslau^. As the result of his researches in this direction, 

 the latter anatomist concludes that in Squaloraja " we have to do 

 with an ancestral form of the now living Pristidse, a form which, in 

 its development, appears to have advanced beyond the existing Pris- 

 tiophoridse, and also beyond the oldest Rhinobatidse," which he has 

 described from the upper Oolite of Bavaria. 



The vertebral arches were not of sufficient consistency to leave the 

 slightest trace in the fossil state. 



Appendicular Skeleton. — In the subject of fig. I, as already 

 remarked, the pectoral fins are sufficiently well preserved to exhibit 

 their complete severance from the cephalic region and their corre- 

 spondence in general character to those of the living Pristiophorus, 

 But the remains of the supporting girdle are much less perfect and 

 satisfactory, and the other known specimens do not appear to throw 

 any further light ui)on the subject. There can be little doubt, how- 

 ever, that the " girdle " was complete, as in the Rays proper, and the 

 well-defined cartilage (s.sc) on the right is evidently the character- 

 istic suprascapula. A faint trace of the posterior boundary of the 

 transverse coracoid bar {cor) is also shown on the same side. 



The proximal cartilages of the fin are only two in number, and 

 well preserved on both sides of the fossil, though most completely 

 displayed on the left. Tlie preaxial element {ptns) is elongated in 

 a transverse direction, and appears of almost uniform breadth, though 

 its exact shape is evidently destroyed by crushing ; it is relatively 

 small, having only about one quarter the size of the postaxial ele- 



^ 0. Hasse, 'Das natiirliche System der Elasmobranchier,' allgemeiner 

 Theil (1879), p. 44. 



" The caudal region of the fossil is not completely shown in fig. 1. 



' 0. Hasse, " Einige eeltene palaontologische Funde," PalsBontographica, 

 vol. xxxi. (1886) p. 4, pi. i. figs. 2, 3. 



