GEOLOGY OF SELBORNE. 377 



a warm, forward, crumbling mould," and of the "white 

 malm " as "becoming a manure to itself." The qualities here 

 alluded to and the general fertility of these particular soils 

 depend on the existence, in addition to lime, of a large per- 

 centage of soluble silica and minute quantities of the alkalies 

 and phosphates in the rocks which produce them. 



In this bed are found ramose Sponges, Ventriculites, Choa- 

 nites, and many traces of other species of the lower organisms, 

 a Micraster, Pecten orbicularis and quinquecostata, several 

 Lamellibranchiates, Pleurotomaria, and Cephalopoda ; the 

 last rare (the Alton Museum contains but one specimen, an 

 imperfect Am. varians). 



In the Upper Greensand a few traces of plants and bored 

 wood are met with. It contains several species of Sea-urchins, 

 and I have a single specimen of the Starfish from the Sel- 

 borne Firestone. Brachiopoda are rare, the Mollusca nume- 

 rous. The Alton Museum possesses about twenty species of 

 Lamellibranchiata, five of Gasteropoda, and ten or twelve of 

 Cephalopoda. The Pecten orbicularis is the only species of 

 which the individuals are abundant. The Cephalopoda form 

 the most conspicuous feature amongst the organic remains of 

 the Upper Greensand of Selborne. Baculites and Hamites 

 are rare, Ammonites numerous (the species rhotomagentis, 

 varians , rostratus, catillus, and probably three or four others). 

 Nautilus pseudo-el eg ans and a larger one (probably a distinct 

 species, sometimes fourteen inches in diameter) are not un- 

 common. 



The Am. rostratus presents three forms of the rostrum, 

 which may indicate specific differences. The shells of the 

 Cephalopoda are mostly found pressed more or less out of 

 their natural form. 



The Belemnitella are rare ; they present a delicate na- 

 creous covering. Some imperfect remains of Crustaceans, a 

 few fish-scales and teeth of fishes and saurians have been ob- 

 tained from the Malm rock. 



The Gault is so little exposed that I have obtained very few 

 fossils from it, and none from the Lower Greensand, within 

 the bounds of Selborne parish. 



w. c. 



