96 



422. A vertical transverse section of a vertebral body of the Lamna cornubica. 



A vestige of the concentric cylinders may be discerned near the centre of the body ; but 

 the chief part of the intervening osseous matter is so disposed as to connect the articular cones 

 in the form of longitudinal converging plates, with interspaces, which are filled with clear 

 cartilage hi the recent vertebra, but form vacuities in the dried specimens. 



Presented by Prof. Owen, F.R.S. 



423. A vertebral body of the Lamna cornubica. 



There are fewer and wider interspaces between the longitudinal osseous plates in this 

 species than in the Selache maxima ; the widest spaces being the two marked () which 

 support the neurapophyses, and the two marked (p) which support the parapophyses in the 

 entire vertebra. 



Presented by Prof. Owen, F.E.S. 



424. The upper and lower jaws of a Shark (Odontaspis) : some of the exterior teeth 



have had their crowns broken off. Mus. Brit. 



425. The upper and lower jaws of another species of Odontaspis, in which the teeth 



are characterized by a small accessory point on each side of their base. 



The inner walls of the jaws have been removed near the symphysis of each, to show the 

 series of successional teeth. The teeth decrease in size from this part to the angles of the 

 jaws, where they lose their points and become adapted by their numbers and close arrange- 

 ment for a coarse mastication of the food. 



Hunterian. 



426. The upper and lower jaws of a nearly allied species of Odontaspis. Mus. Brit. 



427. The upper and lower jaws of a Shark (Galeolamna Greyi) from South Australia ; 



the teeth in the upper jaw resemble those of the Galeus ; those of the lower jaw 

 are intermediate in form between the teeth of Lamna and Carcharias. 



Presented by Governor Grey. 



428. A vertical section of the lower jaw, and of one of the vertical series of teeth of 



a large Shark (Lamna Latro). 



It shows the progression, calcification and consolidation of the teeth as they approach the 

 alveolar border of the jaw. One tooth is erect, and a second and third are in positions inter- 

 mediate between the erect and the recumbent teeth : these are covered by a duplicature of 

 the thick mucous gum. The exterior layer of each tooth consists of a modification of dentine 

 as hard as enamel, called ' vitrodentine.' 



Fig. in Owen's Odontography, pi. 5. fig. 1. Presented by Prof. Owen, F.R.S. 



