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And finally, Sir C. Lyell, long ago, described a locality in Tennessee, 
where the Mammoth was discovered, together with Mastodon ohioticus, and 
existing shells, in a swamp formed in a cavity of the boulder formation. 
These are a few facts in the life-history of this animal. Surviving 
through two distinct periods, Geoffrey St. Hilaire suggested for it the 
name of Dicyclothenum. Much information on this and other topics 
has lately been given by Dr. Falconer, in a discursive paper on an 
American fossil elephant. 
Mr. Salter has described many new Phyllopod Crustacea from the palaeo- 
zoic rocks ; and with a view to show what bearing these have on the 
doctrine of transmutation of forms, has given a diagram exhibiting side 
by side the several genera found in palaeozoic strata. Earliest in time 
comes the Hymenocaris , found in Lingula flags. This genus is charac- 
terized by a carapace in one piece, bent over the body. In the super- 
imposed Cambro-Silurian, the order is represented by Peltocaris, a form 
with the circular shield or carapace in three pieces — that is, two equal 
valves, with a semicircular piece inserted between them covering the head. 
Between this and the previous form there is no relationship whatever. 
Peltocaris is succeeded in the Upper Silurians by Ceratiocaris, which is also 
in three pieces, but the valves differ much in shape, and the relation of 
the wedge-like rostral piece is different. However, there is that close 
affinity that would induce a comparative anatomist to predict the dis- 
covery of intermediate genera when the rocks shall be better explored. 
In the Devonian strata the genus is Dictyocaris, a form quite unlike the 
preceding, with a carapace in one piece, and bent, which seems very 
nearly to reproduce Hymenocaris of the old Cambrian rocks. 
In the Lower Carboniferous, occur Ditliyocaris, and the nearly allied 
genus Argas. Argas is a form very like Ceratiocaris, with the valves 
separate, but it appears to want the rostrum ; Ditliyocaris appears to have 
had a rostrum, but in it the valves were soldered together. 
Then in the Trias we find the recent genus Apus, which resembles 
Dictyocaris, but not very closely. So there are, on the one hand, Hyme- 
nocaris, Dictyocaris, and Apus, forming a sort of natural succession, on 
which Mr. Salter remarks that, “ Apus is unquestionably the most highly 
developed ; and it is the latest.” And on the other hand, Peltocaris, 
Ceratiocaris, Argas, and Ditliyocaris, forming a sort of harmonic pro- 
gression, in which the rostrum gets gradually less important, and the 
carapace more concentrated. We should consequently regard Ditliyocaris 
as probably the most highly organized of this group. And it is worthy 
of remark that that genus is more nearly related to Apus than is 
Peltocaris. 
The facts are few, but they appear to indicate a method or plan in the 
succession of life on the earth. 
Geology has lately lost in Mr. Lucas Barrett one of its most accomplished 
students. From his earliest years there had been a great fondness for 
natural history specimens, and even at an early age a faculty for original 
observation was active, for at school he discovered a layer in the chalk rich 
in univalve shells, and the specimens there gathered served as a nucleus 
for a monograph of chalk gasteropods, long afterwards commenced for the 
