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364 REVIEWS AND BOOK NOTICES. 
there, eighty-five of them being regarded as common. Mr. Trippe 
calls attention to the fact that all but fifteen of the species he 
found breeding in abundance in Southern Iowa, breed also abun-| 
dantly on the Atlantic coast, in the saime latitude, nearly fifteen 
hundred miles to the eastward. This he considers as an astonish- 
ingly small difference, considering the great distance between the 
two points. Although perhaps surprising at first sight, when 
taken in connection with the fact of the considerable differences 
in the faunæ of localities separated by only two or three hundred 
miles in latitude, it finely illustrates certain general laws of geo- 
graphical distribution, namely, that difference in longitude has per 
se, almost nothing to do with the limitation of habitat, while a 
slight difference in latitude, being necessarily accompanied by dif- 
ferences of temperature, is a powerful modifying cause. In other 
words, that species are limited in longitude by climatic and other 
differences in the conditions of environment resulting from the 
configuration of the general surface of the country, and not by 
distance merely. Mr. ‘l'rippe’s list is accompanied with valuable 
notes relating to the season of occurrence and relative abundance 
of the species. —J. A. A. 
New Avian Suncrass.* — The recent discovery of Ichthyornis 
dispar, and Apatornis celer, is one ranking in interest, and impor- 
tance with that of the Archwopteryz; an important gain to paleon- 
tology which, as Prof. Marsh observes, ‘* does much to break down 
the old distinctions between Birds and Reptiles, which the Archwop- 
teryz has so materially diminished.” With just appreciations 
of the value of the characters presented, the writer proposes for 
the birds an order Ichthyornithes, and a subclass Odontornithes. 
The vertebra were amphiccelian, and there were numerous, small, 
compressed, pointed teeth, distinctly socketed, in both jaws. If 
Prof. Marsh’s surmise, that the Archeopteryx likewise had teeth 
and biconcave vertebrie, should prove true, a question of synony- 
my with Saururæ might arise. In explanation of the improper 
allocation of Ichthyornis (in the Key to North American Birds), 
among ordinary natatorial types, it should be stated that informa- 
tion of the discovery was received just as the pages were going to 
pegs, and in advance of Prof. Marsh’s final determinations. — 
* Ona New Subclass of Fossil Birds (OpoNTORNITHES). By O. C. Marsh, “ American 
Journal Science and Arts,” v, Feb., 1873 (pub. Jan 21, 1873). 
