80 



347. The upper and lower jaws of a large species of Diodon, from Sumatra. Part 



of the left maxillary bone has been broken away. Hunterian. 



348. The premaxillary and maxillary bones of a large Diodon. Hunterian. 



349. The premaxillary and left maxillary bones of a large Diodon. 



The pulp-cavity of the lamelliform teeth of the crushing tubercle is laid widely open, and 

 the upper finely-reticulate surface of the last-formed plate is exposed. A vertical section has 

 been attempted, apparently by the common saw, which has been arrested at the dense den- 

 tine of the crushing tubercle, which the saw has not been able to penetrate. 



Hunterian. 



350. The premaxillary and maxillary bones of the Diodon. 



The outer alveolar border of the beak-shaped premaxillary has been removed to expose the 

 germs of the denticles, which coalesce to form the adamantine dentigerous coating of the mar- 

 gin of that bone. 



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



351. The preinandibular and articular pieces of the lower jaw of the same Diodon. 



Fig. in Owen's Odontography, pi. 38. fig. 1. Presented by Prof . Owen, F.R.S. 



352. A similar specimen, vertically bisected, to show the order of succession and 



superposition of the marginal and larger posterior crushing dental plates. 

 Fig. in Owen's Odontography, pi. 38. fig. 2. Presented by Prof. Owen, F.R.S. 



353. The premaxillary and premandibular bones of a small species of Diodon. 



Hunterian. 



354. The premandibular and articular bones of the lower jaw of a large Diodon. 



Hunterian. 



355. A dried skin of a species of Diodon, showing the bony network formed by the 



overlapping of the triradiate bases of the spiny ganoid scales. The anterior 

 ray in most of these is directed forwards and overlaps the posterior rays of 

 those in advance. Hunterian. 



356. A dried and inflated skin of a species of Diodon, in which the spiny osseous 



scales are smaller and more numerous. Hunterian. 



