W. Shone—Crateriform Sand Dunes. 323 
There can be no doubt that a morphogenetic classification and 
nomenclature embodying the results of general researches into 
specific development is a material advance, and that all generic and 
sub-generic names which define and record either well-characterized 
phases in actual development, permanently stereotyped as fossil 
genera, must be recognized as valid. Thus we may hope at last to 
arrive at the true filiation of the fossil forms and their living 
descendants. 
It is to the investigations of Friele, Hugéne Deslongchamps, Dall, 
Morse, Brooks, Beyer, Beecher, Shipley, Schulgin, Kowalevesky, 
Lacaze-Duthier, and last but not least to those of Fischer and 
Daniel and Pauline Cihlert that we owe the great advance of our 
knowledge of the genealogy of the recent Brachiopoda. We seem 
to have arrived at a turning-point in the history of the race. 
Vil.—Tue Cause or Craterirorm Sanp Dunes Anp Cwms. 
By Wiittam Suonz, F.G.S. 
T St. Anne’s-on-the-Sea, Lancashire, there are a great number 
of very large sand-hills. They are for the most part crateri- 
form in the centre, from the gyratory movement of the wind in 
stormy weather. There must be some cause, however, which 
determines the course of the wind, for its natural action one would 
suppose should be to carry away dunes by sweeping them before it. 
I believe the initial cause of crateriform sand dunes is rain. ‘The 
dunes are so porous that the rain does not run off the outsides but 
sinks through them, carrying particles of sand with it as it sinks 
to lower levels. This is especially the case when the base of the 
sand-hill rests upon quicksand. The internal abstraction of sand is 
greatest in the centre and least at the sides—hence the formation of 
a central initial cup. 
During the wet season in Sept. and Oct., 1892, I had many 
opportunities of studying such phenomena at St. Anne’s-on-the-Sea. 
In one instance I was fortunate enough to observe one of these 
rain-made hollows formed. It occupied the centre of a deep crateri- 
formed sand dune. It was forty-eight inches in diameter and twenty 
inches deep in the middle. The centre of the hollow had reached 
the quicksand which underlies the base of the sand-hill. 
Cwms. 
May not the similar action of rain, during a lengthened period of 
time, account for the origin of Cwms. For instance, the beautiful 
Cwm which forms the N.W. front of Cader Idris, in the hollow of 
which lies Llyn-y-Gader. Through the moraine matter which 
stretches across the Cwm, I have heard beneath the surface the 
noise of the surplus water of Llyn-y-Gader rushing away. Rain is, 
I think, the Cwm maker as well as the crateriformed dune maker, 
and both are the effects of sub-erial denudation and subterranean 
erosion acting in unison. 
