1912] 



Miller: Pacific Coast Avian Palaeontology 



101 



groups as the Struthiones and the Stereornithes are in question, 

 it would seem that the chief value of Cope's discovery is to 

 show us that a group of gigantic terrestrial birds can inhabit 

 a region and leave almost no trace of their occupation of that 

 part of the globe. The same fact is pointed out by Eastman 31 '' 

 in his discussion of Struthiolithus and the distribution of the 

 Dromaeognathae. Before the discovery of this species in the 

 superficial deposits in the mountainous regions of northern 

 China no one would have surmised that this great area to the 

 north of India was ever inhabited by struthious birds. Why not 

 expect, then, with perfect propriety, that some day the path of 

 immigration of BJtea into South America may be traced in yet 

 undiscovered deposits of North America? 



The other principle which encouraged the search for rheaids 

 in the asphalt, that of a northward migration of southern forms 

 in the Pleistocene, is applicable whether Rhea be considered a 

 product of the southern continent or not. Among mammals we 

 have the northward diffusion of the various edentates and 

 Hydrochoerus, which may be considered products of southern 

 soil, and we have also a re-entrance from the south of certain 

 forms which are Neogaeic by adoption. For example, we may 

 look upon Didelphys as having performed such migration. The 

 objection might be raised that the tropical belt would act as a 

 barrier preventing the plains-dwelling Rhea from retracing its 

 steps, but such an objection is reduced to questionable validity 

 by the presence of true rheids in the cavern deposits of Brazil. 



The following is a list of lipotypes which are considered by 

 the author as of particular interest : 



List op Lipotypes 



Gavia, sp. 



Gyparchus papa Auct. 

 Thrasaetus harpya Auct. 

 Polyborus cheriway (Jaquin) 

 Cracidae — all species 

 Columbae — all species 

 Psittaci — all species 



Palamedeidae — all species 

 Cariamidae — all forms 

 Phororhacidae — all species 

 Gaura, sp. 

 Plegadis, sp. 

 Ajaia, sp. 



Geococcyx californianus (Lesson) 



3« Eastman, C. R., Bull. Mus. Comp. Zool. Harvard Coll., vol. 32, p. 

 127-144, 1898. 



