DinococJilea ingens from the Wealden Beds, Hastings. 247 



Sj^ecimens jyresent. — Of the dextral form the principal individual 

 is represented by the apex, consisting of the nuclear and first and 

 second whorls ; a portion of the fourth (1) ; part of the seventh with 

 the eighth and part of the ninth ; the eleventh, twelfth, and 

 thirteenth, with a part of the fourteenth ; part of the fifteenth, most 

 of the sixteenth, and the whole of the seventeenth to twentieth, with 

 part of the twenty-first ; the penultimate (? twenty-second) and 

 body-whorl. There arc four sets of two or three whorls each that 

 do not accord with the foregoing, or each other, and may be taken 

 to represent portions of other individuals, especially since in some 

 of them the whorls are distinctly less convex. Several whorls (one 

 more convex), or fragments of whorls, are also present. 



Of the sinistral form there is an apex, consisting of the nuclear, 

 the first six whorls and part of the seventh, with portions of what 

 probably are the tenth to the twelfth and the thirteenth to fifteenth 

 whorls of the same specimen ; there is also a surface portion of a 

 further group of three whorls of very irregular widths, which might 

 correspond to the thirteenth to fifteenth whorls of another individual; 

 and finally a big example of three or four whorls (already alluded to) 

 attached to a concretionary mass of rock, in which the presence of 

 yet two other whorls is traceable, a ad probably coming somewhere 

 about the twelfth to sixteenth whorls of a distinct individual. 



Notes on the Nature of the Containing Rocks. 



By W. Campbell Smith, M.C, Sec.G.S., of the British Museum 

 (Natural History). 



Published by permission of the Trustees of the British Museum. 



The " bluestone " which is found in the central parts of some of 

 the concretions associated with the large spiral bodies described by 

 Mr. B. B. Woodward is found, on microscopical examination, to be 

 a calcareous sandstone. Sabangular grains of quartz, averaging 

 0-04 mm. in diameter, constitute over 50 per cent of the rock, and 

 are set in a cement of carbonates which have crystallized in plates 

 very much as in the Fontainebleau sandstone. These plates are 

 sometimes 3 cm. across, and give a characteristic lustre to the stone. 

 The quartz-grains are evenly distributed through the plates of 

 crystalline carbonate, and are so closely packed as to be almost 

 in contact. It is easy to imagine that A'vith the complete removal 

 of the carbonates by solution there would remain a friable sandstone, 

 very porous, but still occupying almost the same volume as the 

 bluestone. 



In the bluestone 35-6 per cent of the rock is soluble in dilute 

 hydrochloric acid, and contains 17-82 per cent CaO, corresponding to 

 31-82 per cent calcium carbonate, and 2-58 per cent FcoOg, probably 

 present as 3-74 per cent of FeCOj. Insoluble material consists of 

 about 61 per cent quartz and 3 per cent insoluble silicates. The 

 density of the rock is 2-62, very slightly less than the density 

 calculated from its comporents (2-72), showing that the pore-space 

 in the bluestone is very small indeed. 



