IN. PGE, OAGRO AN: 
Ir has ceased to be a startling fact that, prior to the advent of man, a long series 
of ages had rolled by, during which numerous races of plants and animals succes- 
sively originated and became extinct; and we no longer doubt our power to unveil 
the past, even to the period when the encrinite, the trilobite, and the brachiopod, 
were the sole representatives of life upon our planet. 
In the earliest known palozoic rocks, remains of invertebrate animals only 
have been found, and fossil fishes are first discovered in the upper Silurian forma- 
tions. Recently, remains of reptiles have been detected in the Old Red Sandstone 
of Morayshire, Scotland,’ but it was not until the middle of the Secondary Period 
that this class of animals appears to have reached the acme of its development. 
The era of the origin of birds will probably always be involved in more obscurity 
than that of the other vertebrata, as, from their physical construction, their remains 
are the least likely to be preserved. With the exception of footprints, supposed 
to be those of birds, but which may yet prove to be of reptiles, in the sandstone 
and conglomerate of the valley of the Connecticut, no truly characteristic remains 
of the former class have been discovered in any of the primary or secondary fossili- 
ferous strata. 
Of mammalia, a few undoubted remains have been found even as low in the 
geological series as the Trias. Prof. Plieninger recently discovered, in the bone- 
breccia of Wiirtemberg, two molar teeth, supposed to have belonged to an insect- 
ivorous animal, to which the name Microlestes antiquus has been given.” In the 
same deposit, Prof. Plieninger found several incisor teeth, which he considers to 
have appertained to a species of fish allied to Sargus, and, therefore, proposes for 
the animal the name of Sargodon, but Jaeger suspects they also may have be- 
longed to a mammal, which was allied to the Anoplotherium, Cuvier.* 
In the Stonesfield slate of Oxfordshire, England, belonging to the Oolitic Period, 
seven halves, singularly enough, of lower jaws, have been discovered, which have 
been referred to three species of two genera of insectivorous marsupialia: the Am- 
phigonus Prevostii, Ag.; Amphigonus Broderipii; and the Phascolotherium Buck- 
landit, Owen.‘ 
1 Telerpeton elginense, Mantell: Quart. Journ. Geolog. Soc., 1852, VIII. 100. 
2 Wiirtemb. naturw. Jahresb., 1847, III. H. 2, 164. 
3 Fos. Siiugeth. Wiirtemb., 1850, 139. 
* Jahrb. von Leon.u.Bronn, 1835, 186; Owen: Trans. Geol. Soc., 1841, VI. 47, 58; Brit. Fos. Mam., 
29, 61. 
