414 Symonds — British Fossil Mammals. 



in which the skeletons of land mammalia may have been very rarely 

 preserved if mammals existed ; hut the same argument hardly ap- 

 plies to the Carboniferous strata, in which land reptiles, land shells, 

 and land insects have been detected ; and which afford evidence, at 

 least during the deposition of the coal, of the proximity of land. No 

 mammalia, however, have as yet been detected in any palaeozoic rock. 

 After the Permian period had passed away a great thickness of 

 strata known as the New Ked or Triassic formation were laid down 

 upon the submerged and depressed Palasozoic rocks, and as far as 

 we can judge the New Eed formations were deposited, at least in 

 England, in lagoons or salt lakes. This may account for the pre- 

 cipitation of salt at the base of the Lower Keuper marls, as well as 

 for the entire absence of marine shells and the paucity of animal 

 remains of all kinds, with the exception of a few fish spines, the 

 bones and footprints of a few reptiles, and the carapaces of some 

 minute crustaceans (Estheria), very similar to allied species which 

 inhabit salt lagoons at the present day. The Triassic rocks of 

 England were however submerged, and are covered up conformably 

 by the Ehaetic series, which contain marine shells, a Bone-bed full 

 of the triturated remains of reptiles and fish, and, what is more to 

 our purpose in this paper, the teeth of a small mammal, called 

 Microlestes. The teeth of this animal led Dr. Falconer to the con- 

 clusion that it was a plant-eating marsupial, such as is the existing 

 kangaroo rat, many species of which feed on plants in the wilds 

 and forests of Australia. At all events, up to the present time, the 

 Upper Triassic rocks, which the Club visited to-day at Wainlode 

 cliff, are the strata which have rendered to the researches of 

 geologists the oldest known mammalian relic upon the face of the 

 globe. The remains of this little animal have been found by Mr. 

 Moore in Somersetshire, near Frome, and by Mr. Boyd Dawkins, 

 near Watch et. It occurs also in the Trias of Germany. It is 

 evident that both the Bone-bed in which the remains of this first 

 known mammal were detected, and the Insect-limestone, made 

 famous by the researches of my friend Mr. Brodie, were shore- 

 deposits, and the Insect-limestone, with its thin layers of mud which 

 preserve so beautifully the delicate forms of the soft bodies and 

 wings of insects, is just the stratum where we should have expected 

 to find the bones and teeth of land animals that strayed by the sea 

 shores of the Triassic epoch. But it is not so. Deeper sea beds, 

 with Nautili and cuttle-fish, gigantic marine reptiles, and fishes of 

 the deep, cover up the Insect-limestone at the base of the Lias ; and 

 all the thickness of the Liassic rocks, with a large portion of the 

 Lower Oolites, intervene between the burial-place of the little 

 Triassic quadruped and the Stonesfield slate, which furnishes the 

 remains of the next mammalian animals that are known to the 

 geologists. Now mark the deficiency of the geological record ! 

 Unknown and unnumbered ages must have elapsed between the 

 deposition of the Upper Trias and its imbedded Microlestes, and the 

 deposition of the Stonesfield slate. The hills of the Cotteswolds 

 are piled mass above mass between them, yet not a mammalian 



