DEVONIAN FISHES OF IOWA 211 



notices by Hugh Miller,* whose pioneer work in this field was 

 exceedingly accurate and painstaking, and worthy of being held 

 in grateful remembrance. In fact, nearly all of the more salient 

 characters of the typical genera were ably described by this 

 observer. He called attention to the peculiar dentition of Dip- 

 terus, and pointed out that the two dorsal fins are placed far 

 back, that the paired fins are acutely lobate, that jugular plates 

 occur in place of branchiostegal rays, besides mentioning other 

 details that were afterwards fully confirmed by Pander and 

 others.f His restoration of the head-roof is also more satis^ 

 factory in some respects than any that has since been published. 

 In our own time, the most complete account of the skeletal anat- 

 omy of Dipterus is that of Traquair, whose researches have also 

 enlightened us regarding various related genera. £ 



In the New World Devonian, remains of Dipterus proper are 

 confined exclusively to detached hard parts, such as dental 

 plates, scales, ceratohyals, and calcified labial cartilage. Under 

 these circumstances it is difficult to determine whether teeth of 

 a given form should be retained in the typical genus or referred 

 to Sagenodus, Ctenodus or others having a similar form of den- 

 tition. Newberry was well aware of this fact, and even declared 

 that it was impossible to insist upon rigid generic distinctions 

 in the case of Palaeozoic detached teeth. "By convention," he 

 says, "those found in the Jurassic, Triassic and Permian have 

 been called Ceratodus, those in the Carboniferous Ctenodus, and 

 those from the Devonian Dipterus. The experienced eye will 

 easily discover differences in the groups which are arranged 

 stratigraphically, a predominating type of form or markings 

 associating those of the Devonian with each other, and separat- 



*In the "Old Red Sandstone", "Footprints of the Creator", and "Sketch Book 

 of Popular Geology". 



t Huxley has to say of Miller's observations: "It is much to be regretted that 

 Professor Pander should have been wholly unacquainted with these works [of Hugh 

 Miller] when he wrote his Monograph on the Ctenodipterini, and that he has con- 

 sequently inadvertently failed to do justice to the great merits of Hugh Miller, who 

 made known almost the whole organization of Dipterus, and anticipated the most 

 important part of Prof. Pander's labours in this field." — Mem. Geol. Surv. United 

 Kingdom, 1861, Decade X, p. 14. 



JTraquair, R. H., On the Genera Dipterus, Palaedaphus, Holodus, etc. Ann. 

 Mag. Nat. Hist. 1878, ser. 5, 2, pp. 1-12, pi. 3. — Notes on the Devonian Fishes of 

 Campbelltown and Scaumenac Bay in Canada, nos. 1-3. 1890-93.— The extinct Ver- 

 tebrata of the Moray Firth Area. 1896. 



