Prof. S. H. Reynolds—The Rocks of the Avon Section. 547 
have been met with at various levels throughout practically the 
whole section from the lower part of K, to D,. 
(5)  Brachiopod Timestone. -- Brachiopods associated with 
crinoids are very characteristic of K, and K,. They are abundant 
in horizon 8 and Z,, often forming well-marked bands in which 
Spirifer clathratus and Chonetes hardrensis are the most con- 
spicuous forms. Seminula-bands are one of the most characteristic 
features of the S beds. Productus and Chonetes papilionacea bands 
are frequent throughout S and much of D. The suboolite bed 
(top of C,) is also a strongly marked band of Chonetes papilionacea. 
(6) Bryozoa occur abundantly in the Bryozoa Bed at the base 
of K, and in the upper part of K,, and are met with at various 
levels throughout the whole section. 
(7) The presence of worms is often indicated where Modiola 
phase rocks are met with, thus small spirorbid annelids are common 
in K,, and C,. Tubular bodies probably due to worm borings are 
characteristic of the very white calcite-mudstones of 8, and 8, (a). 
Some of the shales of S, are full ot ‘‘ worm tubes ”’. 
(8) Ostracods are very plentiful wherever the rocks are shaly 
or of the calcite-mudstone type, viz. throughout K, at the top of 
C,, in the lower part of S,, and at certain levels in upper 8,. 
(9) Molluscs do not play an important part, though small 
lamellibranchs and small gastropods are plentiful in certain bands 
in K,,, and Euomphalus occurs sparingly in §,. Small. gastropods 
seem characteristic of Modiola phase conditions, occurring in the 
calcite mudstones of 8, as well as in K,,. 
(10) Elasmobranch teeth and spines are very characteristic 
of the “ Palate Bed” just above the Bryozoa Bed in K,, and of 
the ‘‘ Fish beds” at the top of Z,. 
Oolites occur at the following levels :— 
(1) In the upper part of C,, the Caninia oolite. 
(2) At the middle of 8,, the Seminula oolite. Both these are 
very white rocks and of great thickness. 
(3) Thin bands of oolite occur at various levels in the Con- 
cretionary Beds of 8, and in C,. 
(4) Thick bands of coarse red oolite occur at intervals through- 
out the D beds. ° 
(b) Szliceous rocks. 
Grits are met with only in the D beds (D, and upper part of D,), 
where bands may reach a thickness of 20 feet. Sandy limestones 
are frequent in K,, and K,. Quartz grains occur frequently 
throughout the limestones of the ©, 8, and D beds, and at many 
levels secondary growth has converted them into doubly terminated 
crystals. In other cases the crystals seem to have been formed 
independently of pre-existing grains. Bands of chert due to the 
replacement of the limestone occur (a) near the middle of Z,, 
(b) just below the Seminula oolite, and (c) between the Seminula 
oolite and the Concretionary Beds. Partial silicification (beekite) 
