79 



339. A dried specimen of a smaller Ostraao* COTWK/W. Aftu. Brit. 



340. A similar, hut smaller specimen. Mu*. Brit. 



341. A similar, but smaller specimen. Hmitcria*. 



342. A small dried specimen of a Trunk-fish (Ostracio* mutui), showing the single 



row of small slender subacute teeth in both jaws. )///. Bril. 



Family Gytnnodontida. Globe-fish. 



343. A portion of the cranium of a large Porcupine-fish (Diodo* Hytlrijr). The 

 numbers on the different bones indicate their names according to Table I. 

 The three subequal concavities presented by the basioccipital and the exoc- 

 cipitals for articulation with the centrum and neurapophysca of the atlas, and 

 the wide expanse of the roofs of the orbits, are worthy of note. Huntrria*. 



344. The skull of a Diodoa, with the skin dried on. Hnnlerian. 



345. A mutilated skull of a large Porcupine-fish (Diodoni), with the upper and lower 

 jaws and dental armature. 



The alveolar border* of both jaw*, which are shaped like the beck of the Parrot, appear to 

 be sheathed with a hard adamantine dentine, which swell* behind into a broad convex tritu- 

 rating mass : a cavity it exposed above the upper and below the lower dental tubercle, which 

 contains in the recent fish the persistent matrix for renewing the dental substance. The com- 

 plex nature of this is demonstrated in the following specimen. 



lltmtrria*. 



346. The upper jaw, consisting of the maxillary and prcmaxillary bones, and the pre- 



mandibular part of the lower jaw, of a large Diudon. 



Sections have been removed from the pmnaxillary bone, exposing the pulp-cavities of the 

 marginal denticles which coalesce to form the exposed border of the bone, and of the broad 

 superimposed horizontal plates that coalesce to form the posterior tubercle. 



PreKntrd by Prof. O*x*. F.R.S. 



