Dr. K. Woodward — On Fossil Shells, etc., from Sumatra. 441 



and at last become perpendicular ; of course the top layers will be 

 formed long before the bottom. — T.G.B. 



In a paper on "Columnar, Fissile, and Spheroidal Structure," 

 read before the Geological Society (Q. J. G. S. vol. xxxii. p. 141), 

 the Rev. Prof. Bonney has given a list of examples of columnar 

 structure in non-igneous rocks. Amongst these the altered clay bed 

 in Tideswell Dale 1 most nearly resembles our Gorischstein prismatic 

 sandstones. But the Yorkshire clay prisms are from 1 to 6 inches 

 thick and 8 to 9 feet long (Mello), and the columns themselves are 

 curved, as is common in basalts, etc. 



In addition to the examples mentioned in the paper above referred 

 to, Prof. Bonney now tells me of a columnar sandstone underlying 

 basalt from Johnsdorf, near Zittau, Saxony ; ironstone, columnar 

 from burning, exhibiting bent, wavy and radiating columns, about 

 ■£%" diameter, from South Wales; and columnar sandstone from 

 furnaces in Wales, Staffordshire, and Russia — all of which may be 

 seen in the Museum of University College, London. 



Another good example of this structure was observed by my 

 friend Mr. A. F. Griffith, of Christ's College, last year, near Clermont, 

 Auvergne. It occurs in a pale marl under the old lava flow of 

 Graveneine near its extremity, about three-quarters of a mile from 

 Clermont on the Issoire road. Here a quarry has been opened so as 

 to expose some 12 feet of the lava; beneath this is a zone of 

 porcellanized material, irregularly jointed, and about two inches 

 thick ; and next below comes a layer of diminutive hardened 

 columns 5 or 6 inches in thickness. The better prisms are about 

 4 inches long, and \ inch across ; but others are not more than 

 \\ inches long. Beyond the limits of the lava, the prismoidal clay 

 is seen to pass into a pale freshwater marl. Mr. Scrope 2 has 

 described a similar case near St. Saturnin beneath the lava current 

 of the Puy de la Yache. 



III. — Further Notes on a Collection op Fossil Shells, etc., 

 from Sumatra (obtained by M. Yerbeek, Director of the 

 Geological Survey of the West Coast, Sumatra). Part II. 3 



By Henry Woodward, LL.D., F.E.S., etc.; 

 of the British Museum. 



(PLATE XI.) 



AMONG the Conchifera transmitted by M. Yerbeek, is a specimen 

 of Cyrena. The shell is certainly from a very modern forma- 

 tion, as it retains its translucency and traces of a pale buff colour 

 externally. 



19. Cyrena sinuosa, Deshayes. PI. NI. Fig. 1. 

 Mr. Edgar Smith, after comparing this specimen with recent 

 Cyrence in the collection, observes, "The outline of this valve is 



1 Described by the Bev. J. M. Mello, Quart. Journ. Geol. Soc. vol. xxvi. p. 701, 

 and Geol. Mag. Vol. VII. p. 520. 



2 Volcanos of Central France, p. 92. 



3 Continued from the September Number, p. 393. 



