Dr. R. H. Traquair on the Genus Dipterus. 7 



a large series of specimens reveals the fa,ct that no such suture 

 or groove, indicating an original division of the bone, exists, 

 and that the distinguished Russian palasontologist has again 

 been misled by accidental fractures. This is particularly 

 evident in his figure 13, tab. iii. ; and as regards his figure 12 

 in the same plate, in none of the numerous specimens before 

 me can I see any thing at all resembling the straight deeply 

 indented sutural line which is there represented as dividing 

 the posterior diverging part of the palato-pterygoid into two 

 longitudinal halves. The palato-pterygoid of Dipterus con- 

 sists, then, as in Ceratodus and in Ctenodus^ only of one bone ; 

 and the peculiarity supposed to be characteristic of the first- 

 named genus therefore falls to the ground. A completely 

 isolated example of this bone is preserved in the Hugh-Miller 

 collection, and is figured in the ^ Footprints of the Creator.' 



The same remarkable correspondence between Dipterus and 

 Ceratodus is seen in the structure and configuration of the 

 mandible (PL III. figs. 2, 3, and 4) ; but here also we find 

 that in the Devonian genus ossification is more extensive, 

 and, in addition, a ganoid surface is extensively developed on 

 its outer aspect. The articular element (ar), in Ceratodus 

 not differentiated from the Meckelian cartilage, is well ossi- 

 fied, and presents posteriorly, and looking upwards and back- 

 wards, a deep rounded notch for articulation with the qua- 

 drate. Externally and internally the articular is embraced 

 between the posterior extremities of the splenial {sjp) and of 

 the bone termed in Ceratodus " articular " by Dr. Giinther, 

 ^'angular" by Prof. Huxley, The latter element (ag) has 

 the same relations as in Ceratodus, covering as it does the 

 greater part of the outer surface of the ramus, and passing 

 above and behind into a coronoid process. At the posterior 

 extremity of its lower margin there is, in every specimen I 

 have seen, an appearance as if a small additional piece had 

 fitted on just below the angle of the jaw; but as such an addi- 

 tional piece has not occurred m situ, its presence cannot be 

 afiirmed. The splenial {sp), carrying the mandibular dental 

 plate, is extremely similar in shape, and identical in its relations 

 with that of Ceratodus: its anterior extremity, covered up by 

 tlie matrix in the specimen represented in fig. 2, but visible 

 in other examples^ curves inwards and meets its fellow at the 

 symphysis; so close is the union that I have not clearly 

 detected any suture between them. The front of the mandi- 

 ble presents a shovel-shaped aspect, reminding us at once of 

 that of Cey^atodus ; but whereas in Ceratodus the labial margin 

 is formed by a shovel-shaped expansion of the coalesced 

 Meckelian cartilages, and the right and left pieces of bone, 



