MUSCHEL-KALK, LIAS, AND OOLITE. 2BI 
FisJics of the Miischelkalk, Lias, and Oolite 
Formations. 
The Fishes of the Muschelkalk are either 
peculiar to it, or similar to those of the Lias and 
Oolite. The figure engraved at PI. 27^ is 
selected as an example of the character of a 
family of Fishes most abundant in the Jurassic 
or Oolite formation ; it represents the genus 
Microdon in the family of Pycnodonts, or thick- 
toothed Fishes, which prevailed extensively during 
the middle ages of Geological History. Of this 
extinct family there are five genera. Their leading 
character consists in a peculiar armature of all 
parts of the mouth with a pavement of thick 
round and flat teeth, the remains of which, under 
the name of Bufonites, occur most abundantly 
throughout the Oolite formation.* The use of 
this peculiar apparatus was to crush small shells, 
and small Crustacea, and to comminute putres- 
cent sea-weeds. The habits of the family of 
Pycnodonts appear to have been omnivorous, 
and their power of progression slow.f 
* PI. 27*^. Fig. 3. represents a five-fold series of these teeth on 
the palate of Pycnodus trigonus from Stonesfield ; and Fig. 2, a 
series of similar teeth placed on the vomer in the palate of the 
Gyrodus Umbilicus from the great Oolite of Durrheim, in Baden. 
t A similar apparatus occurs in a living family of the Order 
Cycloids, in the case of the modern omnivorous Sea Wolf, Anar- 
