DEVELOPMENT OP VASCULAR DENTINE. 
41 
So far as I have been able to ascertain by an examination of the teeth of such 
Gadidse as I could procure, true vaso-dentine, tipped with a spear-point of enamel, 
constitutes the teeth of all of the family. In the Pleuronectidae we find the same 
thing, viz. true vaso-dentine tipped with a point of enamel, but the teeth (fig. 10*) 
at their apices hardly differ from unvascular dentine, while their bases are typical 
vaso-dentine. This structure, the true dentinal tubes being in greater or less 
abundance at the apex, exists in the teeth of the Pleuronectidae commonly used 
as food. On the whole we might conclude that, so far as minute structure goes, 
the teeth within the limits of these two families are of one type. A similar agreement 
in minute structure is met with in Sargus, Dentex, Pagellus, and Chrysophrys. 
But one type of minute structure does not run throughout larger groups, such as 
Orders, thus for example, amongst Physostomi the Eels have hard unvascular 
dentine : some Siluroids have true vaso-dentine ; Serrasalmo has hard dentine, at its 
base merging into vaso-dentine (fig. 11*), and the Pike has osteo-dentine. 
And great divergence in minute structure may be found within an Order which 
comprises far fewer genera than the Physostomi. 
Thus amongst Plectognathi, Ostracion (fig. 10*) has a tooth composed of vaso- 
dentine quite devoid of dentinal tubes, while Batistes has teeth composed of hard 
unvascular dentine ; the teeth of Gymnodonts also are built up of unvascular dentine. 
The subject is, however, too large a one for discussion in this paper, and the 
exceeding small number of fishes’ teeth examined as compared with the vast number 
of genera and species comprised in the class, may well make a writer diffident in 
expressing any opinion as to the relation between minute structure of the teeth 
and general affinity. 
Note on some Peculiarities in the Attachment of Teeth in the Gadidce. 
In the course of investigating the development of vaso-dentine in the teeth of the 
Hake, I became acquainted with some facts as to their attachment, which are in 
themselves so interesting that, although not quite relevant to the subject matter 
of the rest of my paper, I venture to append a short note describing them. That 
the predatory angler ( Lophius piscatorius) was furnished with large teeth set upon an 
elastic hinge, so that they may be bent inwards towards the gullet, and when 
relieved from pressure at once spring up again, has long been known. 
But I had not met with any mention of the teeth of the Hake, or indeed of any 
other fish, except Anableps and Pcecilia, being similarly attached to the bone which 
carries them. 
Round the margins of the mouth, both in the upper and lower jaws, the teeth, 
which are sharply pointed and slightly recurved, are arranged in a double row. The 
outer row are strongly anchylosed to the bone ; the inner row are attached by an 
MDCCCLXXVnL G 
