J. A. Douglas — Kew Chalk Crinoids. 357 



Heavy mineral separations have been made from a large number of 

 localities throughout the country. The same minerals occur alike in 

 sands and marls,, in the grits in contact with the Charnian rocks, in 

 the basal breccias, in the Dolomitic conglomerate, and in the Rhsetic 

 sandstones of South Wales. 



The most notable feature is the abundance of garnet, particularly in 

 the coarser sands, and in the basement beds resting on the Charnian 

 rocks. This mineral varies in colour between pink and mauve, and 

 contains a large percentage of iron. In some beds the garnets occur 

 as almost perfect spheres, but in others as very angular fragments 

 with conchoidal fractures. In South Leicestershire the heavy minerals 

 often consist chiefly of garnet, but approaching Charnwood the amount 

 of zircon increases, and on the north and north-east borders of Charn- 

 wood the proportion of garnet is very small. Tourmaline and rutile 

 occur in smaller quantity, but are a constant constituent of all the 

 separations ; they vary much, in size and are sometimes very round 

 and smooth. Staurolite is also common. To these heavy minerals 

 the Charnian rocks no doubt have made their contribution, especially 

 in the case of zircon ; for powdered South Leicestershire syenite 

 yielded rutile and zircon, and abundant perfect zircons were obtained 

 from decomposed Mountsorrel granite ; also the Millstone Grit con- 

 tains tourmaline. But in the main the heavy minerals of the Keuper 

 must have come from some distant source. 



Thus it seems that the Upper Keuper accumulated in a continental 

 basin under desert conditions. Shallow pools and occasional water- 

 flows were a feature of this desert, and much of the greatly worn 

 dust and sand had doubtless been long drifted to and fro, both by 

 wind and by water. 



YI. — A jS'ote on some new Chalk Ckinoids. 



By J. A. Douglas, B.A., F.G.S., University Museum, Oxford. 



(PLATE XYII.) 



rriHE following is a brief account of some minute Crinoid calyces, 

 l_ which appear to have been hitherto undescribed, sent me by 

 Dr. Arthur Eowe, who obtained them from the Micraster cor- 

 testiidinarium zone of the Upper Chalk. 



From the number of specimens it would appear that they are fairly 

 common at certain localities, but I have been unable to detect any 

 traces of arm or stem plates. The calyces are well preserved, and 

 that they are full-grown individuals seems evident from their 

 uniformity in size and solidity. 



Mode of Occurrence. — As I am indebted to Dr. Eowe for all my 

 information as to the localities and horizons at which they have been 

 found, I cannot do better than quote his letter to me on the subject : — 



" A fossil so minute can only be seen on a well- weathered surface of a hard rock, 

 and the only zones where I have found them in situ are those of Rhynchonella 

 Cuvieri and 'Eolaster planus in the Isle of Wight and at Dover. The best way to 

 get them is from flint meal. Practically all I have, with the above-mentioned 

 exceptions, are from that source. It is necessary, of course, to have hollow flints, 

 and these only occur in quantity at a few favoured localities in the zones of Micraster 



