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POPULAR SCIENCE REVIEW. 
putrescent ; decomposition cannot afterwards set in, nor can any unpleasant 
gases be evolved. The valuable fertilizing properties of the sewage are 
likewise all retained, and in its deodorized form the liquid has been applied 
with the utmost success to the soil, producing better crops than had ever 
been known before. 
GEOLOGY. 
One of the most interesting of recent geological discoveries is that of the 
“Limb-lizard ” of the lower Lias, a reptile equalling in size the largest known 
fossil forms. It isnot however its size, but its structures, which are interesting, 
for naturalists are accustomed to believe that every group of animals, com- 
mencing with humble forms, lives on in time attaining higher organiza- 
tion ; and though this example does not materially invalidate that view, it 
shows that reptiles existed near the beginning of the secondary age, of 
highest type, and equal in every way to the well known Iguanodons and 
Hylseosaurs which mark its close. This large land lizard is named by 
Professor Owen, Seelidosaurus and included in the order Dinosauria. 
The teeth of its upper jaw passed with scissor-like action in shutting 
the mouth, outside those of the lower jaw, just as they do in car- 
nivorous mammals. In form the teeth were laterally flattened, 
triangular above the jaw, and notched at the sides, and so pre- 
sented an aspect intermediate between that of the little existing Iguana 
tooth and that of the cretaceous fossil Iguanodon. It is towards this 
latter genus that the whole of its affinities tend, and, like it, it is regarded 
as having been herbivorous. The only part of the head which is 
wanting is the extremity of the upper jaw, and to this much interest 
attaches ; for though the skull found shows that the nostril was not near 
the eye, as in the associated Ichthyosaurs, but at the extremity of the 
snout, it remains for the wanting fragment to determine whether it will 
be single, as in the crocodile, or double, as in lizards. 
Very little is yet known of the Jurassic land reptiles. One of the 
undescribed forms from the Kimmeridge clay is a monster with solid limb- 
bones, and unguiculate feet, which could not have measured less than a 
yard in length. 
Dr. Dawson has lately communicated to the Geological Society an inte- 
resting discovery in the coal measures of Nova Scotia, of a species of land- 
shell, in abundance, of the genus Pupa. It is found in the under clay con- 
taining the Stigmarian roots of the Sigillaria. The same species was again 
found more than twelve hundred feet higher up in the series, indicating 
that it had survived numerous oscillations in the level of the land, and the 
growth and decay of at least twenty forests. Of more importance than 
the duration of the species is the permanence of the genus, which is, in all 
essential points, the same that now lives abundantly in the grass of our 
meadows — a duration of time comprising at least three-fourths of all that 
geology makes us cognizant of, not having sufficed to produce in it a single 
change. 
