62 Geological Society. 
especially as indicated by the structure of the teeth, which he 
showed to resemble those of Microlestes, from the Keuper of Wiirt- 
temberg and the Rheetic of Somersetshire, and those of the Oolitic 
genus Stereognathus, the former having on each tooth two multitu- 
berculate ridges, and the latter three ridges, but with only two 
tubercles on each. ‘The fossil presents no characters to show 
definitely whether the animal it represents was a placental or a non- 
placental mammal. 
2. “ Cranial and Vertebral Characters of the Crocodilian Genus 
Plesiosuchus, Owen.” By Prof. R. Owen, C.B., F.R.S., F.GS. 
In this paper the author, with the view of showing that the 
Kimmeridgian Stenecosaurus Manselii, Hulke, really forms the type 
of a distinct genus, discussed the characters by which Cuvier divided 
the fossils referred by him to the Crocodiles into three principal 
groups, to which Geoffroy St.-Hilaire gave generic names, and those 
by which the latter author afterwards distinguished his genus 
Steneosaurus, including Oolitic forms, from the Liassic genus T’cleo- 
saurus. From his exposition of these characters the author con- 
cluded that the above-named species does not belong to Steneosaurus, 
Geoff., and he proposed to make it the type of a new genus, Plesio- 
suchus, characterized by the convergence of the frontal bones to a 
point nearer the apex of the skull than in Steneosawrus, by the ex- 
tension of the gradually attenuated nasal bones into a point pene- 
trating the hind border of the nostril, and by other peculiarities of 
the skull, teeth, and vertebre. The author pointed out that this 
form, like Stencosaurus, helped to bridge over the space between the 
Liassic Teleosaurs and the Tertiary and recent Crocodiles, even ap- 
proaching nearer to the latter than the older Oolitic type. 
3. **On some Tracks of Terrestrial and Freshwater Animals.” 
By Prof. T. M*Kenny Hughes, M.A., F.G.S. 
The author’s observations have been made on certain pits in 
the district about Cambridge which are filled with the fine mud 
produced in washing out the phosphatic nodules from the “Cam- 
bridge Greensand ’—a seam at the base of the Chalk Marl. As the 
water gradually dries up, a surface of extremely fine calcareous mud 
is exposed. ‘This deposit is often very finely laminated, and occa- 
sionally among the lamine old surfaces can be discovered, which, 
after having been exposed for some time to the air, had been covered 
up by a fresh inflow of watery mud into the pit. The author de- 
scribed the character of the cracks made in the process of drying, 
and the results produced when these were filled up. He also de- 
scribed the tracks made by various insects, indicating how these 
were modified by the degree of softness of the mud, and pointed out 
the differences in the tracks produced by insects with legs and elytra, 
and by Annelids, such as earthworms. ‘The marks made by various 
worms and larve which burrow in the mud were also described. 
