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rorULAR SCIENCE REVIEW. 
formed by the conceutric shell-layers that envelop the siphons, and, on the 
surface, by the mantle and other soft parts. This median elevation is 
smooth, having no impressions of muscular parts, and is deeply concave 
along the median axis. The lateral walls of both siphons are contiguous 
to the median axis of the valve, and continue as a straight ridge for a con- 
siderable distance down towards the inferior margin of the valve. The soft 
parts that secreted the concentric layers of the siphons, by degrees moved 
downward during the growth of the animal, filling the place they once 
occupied with shelly matter. Thus the apices of the siphons are generally 
found filled with concentric layers. Some faint longitudinal striae are seen 
on the interior walls of the siphons. The concentric layers around the 
siphons form two strata that are quite distinct from the rest of the shell- 
matter, and are embedded in it. They cannot, therefore, the author thinks, 
be confounded witli septa, which, when they do occur in the shells, are in 
immediate contact with the valves, and compactly united with them. The 
siphons of the dorsal valve are shorter than those in the ventral valve, and 
often more divergent. Dr. Lindstrom thinks we gain the true interpreta- 
tion of the nature of these siphons, if we attentively examine the interior 
surface of the valves in the genera Lingula and Oholus. The corresponding 
part of the valve of Lingula being occupied by two impressions of the ad- 
ductors, situated on each side of a broad, faint, shield-like elevation. Though 
in some points he admits the relation between Trimerella and the Lingulidcej 
he thinks there are many features, especially characters of the dorsal valve, 
which widely separate it from this family. The valves, he states, attain 
a thickness of fifteen millimetres, and consist in their perfect state of cal- 
careous spar. 
Chemical Geology. — Mr. David Forbes, F.R.S., has sent us a very interest- 
ing paper (reprinted from Chemical Netos, Oct. 23) on some points in Che- 
mical Geolog}’. Tn this Mr. Forbes deals in trenchant and forcible language 
and conclusive logic with the question of the constitution of the earth. 
Criticising M. Delaunay’s late memoir before the French Academy of 
Sciences, he argues, with M. Delaunay, against the views of Mr. Hopkins and 
Archdeacon Pratt. Ho demonstrates that the reasonings of these writers were 
very correct so far as they went, but that they were based — as not a few 
mathematical reasonings are — on purely arbitrary premisses. Mr. Forbes’s 
paper is one that will be read with the deepest interest, and though his 
conclusions, like many scientific inductions, cannot be accepted as defini- 
tively proved, they certainly appear to us much more on the side of truth 
than those of the opposition. 
The Mi)u-ral nature of Eozoon. — INIessrs. King and Ilowney, persisting in 
their views on this subject, sent in a memoir on the so-called Eozoonal 
rock ” to the Geological Society on Wednesday Dec. 23. 
