208 The American Geologixt. Mmxii, 189:} 
Cretaceous flora. In view of the existence of transitional areas be- 
tween distinct ])lant-fornmtions, it has been attempted to lay the 
ground-work of study of the so-called ^'/^s•/o//-//■/(^'.s• between forest and 
prairie iox example. Certain remarkable peculiarities of a tension-line 
population are pointed out and it is sought to establish a law of 
ejection from the depths of formations, by the action of which the 
tension-line would become the area of the distinctively newer or 
weaker types, and of the types in a highly variable or plastic condi- 
tion. On pp. (i02 and secj. the probable physiognomy of the Creta- 
ceous period is discussed in the light of the tension-line analysis. It 
is argued that the preponderance of metaspermic leaves in the rocks 
by no means indicates a preponderance of metaspermic plants in 
Cretaceous forests, but indeed quite the reverse, since it shows that 
the metaspermic plants were in the proximity of the sandy beaches 
and mud flats, consequently in the tension-line position and prob- 
ably, therefore, established only as narrow, highly variable fringes of 
ejected plants but with great central masses of cycadean, coniferous 
and i)robab!y older types of species forming the isolated bulk of the 
forest population. 
From this study of the ancient physiognomy in the light of modern 
plant-formations a highly ingenious theory of the apparent sudden- 
ness of appearance of metaspermic forms and their great variability 
is developed. A new link between pal;eo])hytology and modern 
geographical botany is indicated, the further examination of which 
may be productive of most interesting results. This interesting and 
valuable report forcibly illustrates the interdependence of the natural 
sciences. 
])isfrlliitli(iii of StoiK' Iiii})l(iiii')its ill the Tide- n ate r cemnti'i/. W. H. 
HoLMK.s. (From the American Anthropologist, Vol. vi. pp. 1-14.) 
Mr. Holmes has introduced a new classification of aboriginal or 
prehistoric stone implements. It has been customary, following Mr. 
James Geikie, of Scotland, to designate as "paleolithic" many rude, 
evidently chipped stones which have been found in Europe and 
America, these being considered as evidence of very low grade of hu- 
man ingenuity and skill, and as "neolithic" those chipped stones whose 
finish indicates that they had a definite purpose, completely attained, 
and shows in their maker a degree of skill equal at least to that of 
the historical aborigines of this country. It hn^ nisoheen presumed, 
in this country, following again Geikie's determinations in Europe, 
that the "paleoliths" were characteristically found in gravel beds, re- 
sulting from the disintegration and rapid withdrawal of the ice of the 
last glacial epoch, and that, therefore, theirjmakers were pre-glacial or 
inter-glacial men. The "neoliths" were, therefore, all classed as post- 
glacial. This has been at least a working hypothesis in America for 
about twenty years, and several "finds" have been reported which 
tended to establish, as interpreted by the fortunate finders, the truth 
of this generalization. 
