322 NOTES ON THE STRUCTURE AND RELATIONS 



of the animal whicli previously had been but ill understood ; 

 but to these I may solicit the attention of the Society at 

 some future time, as my vouchers for a restoration of the 

 animal, which I have some intention of attempting. At pre/- 

 sent I shall merely call the Society's attention to an inte- 

 resting Cromarty specimen of Coccosteus, which presents 

 the head and cuirass in profile, and exhibits the two bones 

 of the under jaw, with their symphysial teeth. But instead 

 of throwing any light on the problem of their position, it 

 merely states the mystery in its extremest form. 



A suite of fossils on the table yields some additional in- 

 sight regarding the structure of the cranium and jaws of 

 Dipterus. The palaeontologist, — even with all the assistance 

 which his science now derives from the optical lapidary, — 

 cannot deal by his fossils as Signor Sarti used to deal with 

 his anatomical models, — raise one layer of bone or integu- 

 ment after another, to show the deeper and still deeper un- 

 derlying parts. He must seek from suites of fossils that 

 exhibit in succession each a deeper and deeper section, in- 

 formation similar to that which the ingenious Italian made 

 a single model convey. I shall exhibit to the Society one 

 of these suites, which my recent labours in the north has 

 well-nigh enabled me to complete, illustrative of the head of 

 Dipterus. We have here the interior of the creature's lower 

 jaw, — a specimen which shows the great strength and depth 

 of the bone at what in other jaws would be the symphysis 

 but where that of the Dipterus had no joining. In this se- 

 cond specimen, the outer side of the jaw is exhibited, and 

 the lines on either side indicated where the three pieces of 

 which it seems to have consisted in the foetal state were 

 united. This third specimen exhibits the jaw bearing its 

 triangular patches of teeth that corresponded with and acted 

 against the triangular patches in the palate. In this fourth 

 specimen, the base of the skull is shown with its palatal 



