50 
THE LOWEK LIAS OF KEYNSHAM 
Avicula : 
Avicula fallax, Pfliicker. {Monotis decussata) from the 
zone of Ostrea liassica. 
Avicula inequivalvis^ Sow. {Av. sinemuriensis^ Oppel) is 
extremely abundant at certain horizons in the upper beds and 
is associated with a mutational form in which the radial ribs 
are almost absent from the large valve. 
Modiola : 
M. minima^ Sow. 
M. hillanoides, Chap and Dew. may be considered to be in- 
termediate between the minima and scalprum types. 
Myoconcha : 
M. scabra, Terq. and Piette. A single fragment from the 
Semicostatus beds. 
Pinna : 
P. hartmanni, Ziet. — Specimens are numerous, but can 
only be extracted with great difficulty ; they are all referred 
tentatively to this species. 
Cucullea : 
A few poor specimens are doubtfully referred to this 
genus. 
Cardinia : 
At certain horizons the beds are crowded with Cardinias^ 
but good specimens are obtained with difficulty. If all the 
Lower Lias Cardinias are arranged under three mutational 
stages, as is done by Dr. Brauns, our Keynsham specimens 
would fall into the two groups indicated by the names C. lis- 
teria Sow. and C. crassiuscula, Sow. Specimens of the first 
type are common in the upper Psilonotus beds and specimens 
of the last are abundant in the Calcicosta beds of the 
Angulatus zone. 
