Yorkshire Naturalists at Dent. 183 
An interesting Mycetophild was the cave-dwelling Speolepta 
( Polylepta ) leptogaster Winn. Others in this group were : — 
Boletina trivittata Mg. 
Anaclinia nemoralis Mg. 
Macrocera fasciata Mg. 
M . stigma Curt. 
M . angulata Mg. 
Platyura nemoralis Mg. 
Apoliphthisa subincana Curt. 
Tetragoneura sylvatica Curt. 
Mycetophila vittipes Zett. 
The few Empids caught were : — 
Trichopeza longicornis Mg. Rhamphomyia flava Fin. 
Rhamphomyia nigripes F. Hilar a maura F. 
R. sulcata Fin. Empis vernalis Mg. 
The most striking of the Syrphids was Sericomyia lappona L., others 
being :■ — 
Chilosia maculata Fin. Rhingia campestris Mg. 
Chrysogaster Macquarti Lw. Sphegina clunipes Fin. 
The curiously marked Dictya ( Tetanocera ) umbrarum L. occurred in 
a place which in its mosses and appearance was almost a replica of the 
places it occurs in at Austwick. 
A Dent Problem (Chris. A. Cheetham) : — Upper Dentdale certainly 
did not give the botanists anything like the easy ecological facts suggested 
by the simple geological structure, the valley bottom is cut in the Great 
Scar limestone and this was seen vividly in Hell’s Cauldron and Black 
Dub, but we were not on limestone country according to the plants. The 
moss men missed such typical limestone ghyll plants as Orthothecium 
intricatum and Plagiobryum Zierii and they decided this was due to a 
lack of moisture on the limestone walls of the ghyll. The botanists 
missed the more typical plants of limestone areas in the fields bordering 
the stream and some explanation seems called for to account for these 
anomalies. The fact is that we were really not in a true limestone area 
such as we are used to in West Yorkshire. Here in Dentdale the lime- 
stone was buried, and it was also very solid in structure. Usually in 
our area we find the Great Scar limestone top above 1000 ft. O.D., full 
of fissures and crevices, allowing all water to pass through it and to issue 
below on the hill slopes under the limestone platform ; this gives a warm 
dry area on the limestone top for plants and plenty of moisture ready to 
issue from the limestone walls, where a gorge has been worn by a stream ; 
but in Dentdale this limestone summit has dipped steeply down until 
it is only 500 ft. O.D. and in the valley bottom. The stream bed shows 
very solid rock over which the water runs freely ; none enters this solid 
structure and so our stream walls are dry. The fields in the same way 
are far less drained and the little lime present in the water has come from 
the thinner limestone bands of the Yoredale sides of the valley, but not 
from the limestone below our feet. Lime may be present in solution 
in the water, but the valley soil owes nothing to the buried mass of Great 
Scar limestone. 
All this is due to the abnormal dip of the rocks ; standing on the top 
of Whernside and looking south we see the limestone scars of Chapel le 
Dale their upper surface some 1200 ft. O.D., then turning north to Dent- 
dale we find this surface in the valley bottom at 500 ft. O.D., a great 
alteration in a short distance, say five miles, and contrary to the normal 
dip to the South-east in other parts of the county. We may see this dip 
and the type of solid rock to advantage in the stream bed beyond Cowghyll 
and by the side of the road to Newby Head, here the absence of cracks and 
fissures is very noticeable, the water running along the surface of the 
dipping limestone bed. 
I 933 August 1 
