64 
highly fossiliferous deposit, between the Keuper and the 
Bunter, unknown in this country, but largely developed in 
Germany. Among the genera, common to both, are Hybodus, 
plicatilis, Saurichthys apicalis, Gyrolepis tenuistriatus, and 
Alberti, (the two latter are Sauroid fish,) Acrodus minimus, 
and Sargodon Tomicus. Other fish such as Ceratodus, Squa- 
loraia and Lepidotus, are also associated with the above ; the 
last has a very wide range, and passes upwards through the 
Lias and Oolites into the Wealden. 
In addition to these facts which gives a special interest to 
this singular deposit, it has another and more important one 
to the Palzontologist, in the occurrence of the teeth of 
Mammalia, which although only indicating a very diminutive 
Mammal, is of great importance as shewing their existence 
at this period. 
Mr. Dawkins discovered a tooth of a Mammal (Hypsi- 
prymnopsis Rheetica) allied to the Kangaroo rats,* in strata 
of this age at Watchet; another has since been found in 
Devonshire, and my friend Mr. C. Moore, has previously 
described a small Mammalian (Microlestes) tooth in detritus, 
derived from these Rhetic beds at Frome in Somerset- 
shire. Previous to these discoveries in England, a small 
tooth (Microlestes antiquus) belonging to this class has 
been observed at Wurtemberg, in Germany, in a bone bed 
of similar date. These are not the earliest indications of 
the presence of Mammalia, because a small tooth Dromathe- 
rium sylvestre is stated to have been detected in the new 
Red Sandstone in America, which is so far the earliest proof 
yet known of any animals of this high class, but it would 
not be surprising if others were found in still older 
formations. 
ed Be EE eS ee eS Se 
* This interesting tooth was found by Mr. Dawkins, at Watchet, in the grey 
marls beneath the ‘bone bed,’ and therefore strictly speaking, is somewhat older, 
and are classed by him as lower Rhetic, Proceedings Geological Society, 1864, 
