graptolites; the other calcareous, with brachiopods, trilobites, andc.
The sub-divisions of the system may be grouped as follows: (I) Ceratopyge Limestone; (2) Lower GraptoliteShales and Orthoceras Limestone; (3) Middle GraptoliteShales, Chasmops and other Limestones, Trinucleus beds.
England and consists partly of graptoliteshales, partly of limestones and sandstones.
