NO. II CLASSIFICATION, BIRDS OF THE WORLD — WETMORE 3 



a factor, however, which must remain hypothetical. Steiner's supposi- 

 tion that the London specimen is male and the Berlin fossil female 

 is equally speculative, since if sex is assumed, the reverse might be 

 true. While the male is larger than the female in most living birds, 

 this is not the universal rule, and as reptilian characteristics persist in 

 these earliest known avian forms it must be remembered that in 

 reptiles it is common for the female to be larger than the male. As a 

 further contribution to available information there should be noted 

 the analysis of the primary wing feathers by Savile (1957, pp. 99-101), 

 which points out an apparent difference in wing formula between the 

 London and the Berlin birds. This recent observation if accepted 

 would indicate rather wide separation, but, on the other hand, if denied 

 would serve to bolster the conclusions of de Beer. 



A third specimen found in 1956 near the point where the first ex- 

 ample was discovered shows mainly wing and leg bones and vertebrae, 

 in addition to feather impressions. It has been described in detail 

 by Heller (1959, pp. 1-25), who finds that it agrees in size and char- 

 acters with the one in London, so that there are now two of the 

 larger form known. 



It is important to have a modern study, like that of de Beer, of 

 the Berlin specimen, to add to the data assembled by Dames. As 

 matters stand, the three known skeletons present an appearance of 

 differences sufficient to mark them as two distinct species on the basis 

 of criteria found in the osteology of living birds. These data, for the 

 present, appear to warrant recognition of two genera, Archaeopteryx 

 represented by two specimens and Archaeornis by one, which, how- 

 ever, should be united in one family, the Archaeopterygidae. 



Ichthyomithes. — A recent study by Gregory (1952, pp. 73-88) has 

 severed the long-standing association of Hesperornis and Ichthyomis 

 in a superorder separated from all other birds known from the New 

 World through the possession of teeth. In brief, Dr. Gregory has 

 shown that the toothed lower jaw fragments allocated to the skeleton 

 of Ichthyomis dispar Marsh, unduly large in proportion to the rest 

 of the skull and the skeleton with which they have been associated, 

 in reality are not avian but are those of a small mosasaur. Two other 

 jaw fragments placed by Marsh with Ichthyomis anceps and /. victor 

 are similar, so that all these specimens, which have the teeth in sockets, 

 are identified as reptilian. This leaves Hesperornis as the only group 

 of Cretaceous age in which teeth are known. To give a balanced 

 treatment that will emphasize the important characters of the birds 

 concerned it has seemed appropriate to establish a suborder Ichthy- 

 ornithes for the Ichthyornithi formes, separated from all other birds 



