British Fossil Birds. 409 



were both derived from a common Avian stock, and have not 

 originated separately from Reptiles. 



The skull of a large bird from the London Clay described 

 by Sir R. Owen in the ' Trans. Zool. Soc.' vol. vii. (1869) as 

 Dasornis (correctly Dasyornis) londiniensis , and referred to 

 the Ratitse^ appears to indicate a bird allied to Gastornis. 

 Since, however, this skull differs to a certain extent from an 

 imperfect example of that of the latter genus obtained by 

 Dr. Lemoine from Rheims, it affords evidence that the large 

 British Ratite bird of the London Clay was generically dis- 

 tinct from its ally of the underlying "Woolwich and Reading 

 beds. 



V. Birds of the Cretaceous. 



The well-known coprolite-beds of the Cambridge Green- 

 sand yielded so far back as 1858 not only the first evidence 

 of Cretaceous birds, but also of the existence of the Avian 

 class in the Mesozoic period. These remains were at first 

 referred by Prof. H. G. Seeley to two genera, nnder the 

 names of Palaocolymbus barretti and Pelagornis sedgwicki. 

 The second generic name was, however, preoccupied, and 

 when the specimens were subsequently described in the 

 ' Quart. Journ. Geol. Soc' for 1876, both species appeared 

 under the name Enaliornis ; but it may be questioned whether 

 the substitution of this name for Palceocolymbus was not 

 ultra vires. 



Like all the remains from the Cambridge Greensand, the 

 bones of Enaliornis are for the most part more or less broken 

 and water- worn fragments ; the most satisfactory specimens 

 being examples of the distal end of the femur and tarso- 

 metatarsus. Both the latter bones approximate so markedly 

 to the corresponding portions of the skeleton of the Divers 

 {Colymbus) that there can be but little hesitation in regarding 

 the bird to which ■ they belonged as more or less remotely 

 allied to that genus. The tarso-metatarsus approximates to 

 that of the Colymbidce in its lateral compression, in the 

 equality in the size and length of the third and fourth trochleas, 

 and in the shortness and extreme reflection or the second 



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