54 (Review of decent Geological Literature. 
man has been to correct the estimates of geological time. Let 
the discussion go on. Let us not discourage it even by the 
suggestion that it is beneath the dignity of the true geologist 
to make estimates of geological time in years. 
REVIEW OF RECENT GEOLOGICAL LITERATURE. 
Considerations $ur lesfossiles decrits conime Algiies. Bj G. Maillard. 
(Abhandl, Schweizer, Paleontol, Gesell, vol. xiv. 1887. Basel and Gen- 
eva, pp. 1—40, pis. i — V.) 
One of the most valuable contributions which has lately been made to 
paleontological science is that of M. Maillard, curator of the museum of 
Annecy, on those fossils described as algpe. 
After reviewing briefly the history of the synonymy of these organisms, 
so many of which are "problematic," the author divides them according 
to superficial characteristics into two categories: 
I . Those in the form of simple semi-cylindrical or more or less flattened 
elevations occurring on the lower surface of the strata, and which are 
identical with the matrix in chemical constitution, grain, and color, 
■without any mixture of a foreigyi substance peculiar to the presence of the fos- 
sil; they cannot be isolated from the strata, but comprise simple contour 
or bas-reliefs on the under side of the strata. These forms which he 
calls "demi-reliefs" include (a) most of the palieozoic forms, such as 
Crossochorda, Cruziana, Harlania, with perhaps Spirophyton and Alec- 
torurus; (b) Helminthopsis, Gyrochorte and Cylindrites in themesozoic; 
(c) the Helminthoidne, Palsodictyon, and Munsteria in the Tertiary. 
The second category includes those which may be isolated from the 
rock, and which are more often cylindrical or membranaceous, evidently 
more or less flattened by pressure, and whose composition differs some- 
what from that of the matrix by the presence of some foreign substance 
which is confined to the fossils themselves, or at least is found in a 
smaller degree in the surrounding matrix. Such are (a) in the Juras; 
sic, Chondrites, Theobaldia, probably Discophorites and Gyrophylites, 
Taonurus (Cancellophycus and Zoophycus), Nulliporites (Chondrites) 
hechingensis; (b) Chondrites, Taonurus, Caulerpa, Sphaerococcites, Dis- 
copharites and Gyi'ophyllites in the Cretaceous ; and (c) in the Tertiary, 
Chondrites, Caueerpa, Taenidium, Halymenites, Hormosira, Sphierococ- 
cites, Gyrophyllites, Nulliporites, Aulacophj'cus, and Taonurus. The 
author calls especial attention to the fact that these two classes are quite 
distinct and that there is no transition between them, thus indicating a 
different origin. 
