78 VAUGHAN : A NOTE ON CARBONIFEROUS SEQUENCE. 
On the other hand, in the case of the CUsiophyUids, 
structural variation can be studied with ease, and the increase 
of complexity, as we progress through the Dihunophyllu7n-Zone, 
is convincingly exhibited ; for example : — 
Dihunophylla , of the 0 stage in D^, reach the xj/ stage in D^. 
Konickophylla in D^, become Acrophylla in D^. 
Clisiophylloid Lithostrotion in leads on to Lonsdaleia 
in D^. 
In fact, the employment of the Clisiophyllids, rather than 
P. ' giganteus' is comparable wath the use of a delicate balance, 
in place of a clumsy pair of scales. 
Other Exposures of Limestone. 
Two other exposures of the massive limestone were 
hurriedly examined, both situated on the right bank of the 
Nidd. 
In the first, at Lolley Scar Quarry, the limestone underlies 
the fossihferous black shales which are again referred to below. 
The fauna of the limestone appears to agree with that of the 
shales, but very few Brachiopods were observed, and no Corals. 
In the second, near Limley, Petalaxis Portlocki, Campo- 
phyllurn derhiense, and a Dibunophyllid, identical with a form 
which occurs at Greenhow, seem to fix the horizon of the beds 
as approximately on the same level as the Greenhow Quarries, 
that is, in D^. 
The stratigraphical correlation of the several limestone 
exposures can only be arrived at by detailed field work, and 
more material is necessary to complete the faunal survey. It 
is also probable that careful search will bring to light lower 
horizons than any which were examined during the Easter 
excursion. 
II. — The Shales between the Massive Limestone 
AND THE ' Millstone Grit.' 
Black fossiliferous shales w^ere examined at two points : — 
(1) In LoUey Scar Quarry, where they rested immediately 
upon the top of a massive Umestone (v.s.). 
