474 



THE GEOLOGIST. 



is more darkly ferruginous and their texture markedly oolitic or 

 granular, though, not unfrequently they change to a deep green hue, 

 imparted to them by the protoxide of iron, when the granular structure 

 becomes less observable. The fossils, also, which they enclose, though 

 exceedingly distinctive and familiar, have not yet been found in situ 

 at Hotham. They are the common forms of the true Marlstone — the 

 " Spinatus " and Margaritatus " zone of Oppel and Wright— which is 

 shown in typical sections, as at Gretton, near Winchcombe, in Glouces- 

 tershire, to occupy the top of the Middle Lias in the southern counties. 

 I collected here the large Pecten equivalvis and P. corneus, both of 

 which were plentiful as usual, Belemnites, Pleuromya unioides f?J, 

 Cardinia crassissima, and Ammonites Englehardti, with some others. 

 The drift which I have been now considering contrasts remarkably, 

 from its mixed character, with those other and almost homogeneous 

 deposits which have been shown to cover the neighbourhood of Korth 

 Cave. 



III. It may be about 200 yards across the Middle Lias ; but its 

 junction with the rock next succeeding is not well exhibited. The 

 country is now flat to the foot of the chalk, and the sequence of the 

 different rocks that traverse this level is partly undeterminable from 

 lack of sections, and partly obscured by drift, so that I could not make 

 it out with sufficient exactness. I ascertained, however, that the 

 ferruginous beds give place to an inconsiderable band of yellow tenacious 

 clay ; and that this again is apparently succeeded by a still narrower 

 zone of very peculiar marly limestone, which I shall call provisionally 

 the LiGNiFEEous Mael, and describe as fully as my present materials 

 will permit. I regret that these are not more ample, which is owing, 

 in part, to my limited opportunities. I believe this to be an exceptional 

 bed, possibly it may even be unknown hitherto, and unrecorded in our 

 series. Its lithological character might refer it to the Upper Lias ; 

 but its fossils in general, and particularly in one or two instances, are 

 much more of Oolitic than Liassic types ; and consequently I should be 

 inclined, in the existing state of my knowledge, to assign it an inter- 

 mediate place between the Upper Lias and Inferior Oolite, somewhere- 

 in that debatable ground " which has lately received such- 

 elaborate illustration from Dr. Wright. I have reason to suspect the 

 existence of the Upper Lias Clay at Hotham ; and I shall hope to prove 

 that I have seen there the lower portion of the Inferior Oolite^ a little 



