Palaeontologie. 
65 
Udden, J. A., A Cycad from the Upper Cretaceous in Mave- 
rick County, Texas. (Science, N. S. XXVIII. p. 159 — 160. July, 
1908.) 
Describes the discovery of a silicified cycad trunk in the Up- 
son clays of Maverick county, Texas, some 1400 feet above the 
base of the Upper Cretaceous. This is the latest trunk hereto- 
fore found in this country although frond impressions are not rare 
in the Upper Cretaceous. The author does not mention the 
possibility of the specimen having been redeposited from an older 
formation. Berry. 
White, D., Some Problems of the Formation of Coal. (Eco¬ 
nomic Geology III, p. 292—318, 1908.) 
An able discussion of the factors involved in the genesis of the 
various kinds of coal, such as the varieties and relative proportions 
of the organisms involved, their conditions of growth and accumu- 
lation and the dynamic forces concerned in their subsequent alterations. 
Some of the authors conclusions are that the Carboniferous cli- 
mate was humid and extraordinarily equable but not necessarily hot; 
that the plants grew in greatest profusion on an unstable peneplain; 
that some grow on the present site of the coal (autochthonous) while 
others were transported (allochthonous). In the majority of cases, 
however, the former view, that of peat swamps, is the most probable. 
The importance of micro-algae in determining the character of the 
coal is emphasized, the author also holding that the oils and gases 
of the older sedimentaries are derived by pressure-distillation from 
gelatinous micro-algae which were possibly enriched by the decay 
of the Contemporary faunal elements and suggests a like origin for 
the abundant graphite of the pre-Cambrian rocks. 
The conditions of coal formation embrace two principal stages, 
the biochemical or putrefaction stage, and the subsequent dynamo- 
chemical alteration or metamorphic stage. The first was accom- 
plished largely through the vital activity of microorganisms especially 
anaerobic bacteria, while the latter in the author’s opinion is due 
chiefly, not to folding or faulting, but to the deeper-seated horizontal 
thrust movements of which the former are but the expression, com- 
bined with gravity pressure due to loading. 
The degree of de-oxygenation of the organic matter is the true 
index of the progress made in the formation of the coal and it is, at 
the same time, the index of the efficiency of the fuel. Berry. 
Zalessky, M., Beiträge zur Kenntnis der fossilen Flora des 
Steinkohlenreviers von Dombrowa. (Mem. Com. geol. N. S. 
Livr. 33. Russisch (p. 1—38) und deutsch (p. 39 — 63). 10 Textfig. 
2 Taf. St.-Petersburg. 1907). 
Nach einer ausführlichen Besprechung der geologischen Ver¬ 
hältnisse der Pflanzenfundstelle (Russisch-Polen) beschreibt Verf. 
die Pflanzenreste, die aus den Schichten unterhalb und oberhalb 
des Redenflötzes der dortigen Gegend stammen. Es werden u. a. 
angegeben Asterocalamites scrobiculatus, Calamites Suckowi, Spheno- 
phyllum tenerrimum. Bei Gelegenheit der Besprechung der Lepido- 
dendronreste, von denen Verf. Lepidodendron aculeatum, obovatum, 
dichotomum und Tonderae n. sp. beschreibt, kritisiert Verf. die 
Fischer’schen Arbeiten über Lepidodendron; Fischer ist nach Verf. 
Botan. Centralblatt. Band 110. 1909. 5 
