ft. 



in, 



4 







1 







14 











3 



3 







108 H. F. Tomes — Liassic Maclreporaria. 



numerous small glittering crystals of pyrites, small Gasteropoda, 

 fragments of Pentacrinites, and Acrosalenias. 



With a view to determine, if possible, the precise stratigraphical 

 position of the corals, I visited the Dumbleton hill quarry, only three 

 miles distant, still in work, and satisfactorily determined their horizon. 



The following is an accurately measured section, showing the beds 

 at present exposed : — 



1. Surface soil 



2. Fish bed, finegrained and laminated stone, with Saurian remains, 



Lept'depis concent ricus, and insects 



3. Laminated blue shales 



4. Layer of intermittent nodules of hard stone containing fucoids 



5. Laminated blue shale, like No. 3 



6. Whitish grey clay, hard and breaking up into angular lumps, and 



weathering into a soft light-coloured clay 9 



7. Hard light blue shale, in the lower part of which are many Belemnites, 



and in the upper part numerous small cubes of pyrites, small 

 Ammonites {A. Hollaudrei) and Gasteropods 1 3 



8. Friable shale, having the appearance of soft marlstone, brown or 



ferruginous in colour, and sometimes micaceous 1 



9. Middle Lias Marlstone, very fossiliferous 3 



28 3 



All the beds downwards, until we arrive at No. 6, are finely 

 laminated, and it would be time wasted to seek for corals in them. 

 However beds 6 and 7 are wholly different. The first of these, 

 No. 6, is light-coloured and hard, breaking up with the hammer into 

 more or less square or angular lumps. It appears to contain very 

 few fossils. No. 7, like the one above it, is not laminated, but is 

 bluer, softer, and much more fossiliferous. Near to the bottom of 

 it are Belemnites in abundance, and it also contains a great many 

 small specimens of Ammonites Hollandrei. Very near to, or at the 

 top, are a great number of crystals of pyrites, similar to those at the 

 Stanley hill quarry. These two beds weather down into a soapy and 

 disagreeable mud, and this perhaps accounts for their having been 

 wheeled well back on to the top of the waste heap out of the way, 

 both at Stanley and Dumbleton. The corals are much less common 

 at the latter than at the former place, only two specimens having 

 been met with. Both were in close proximity to the layer of pyrites, 

 and in the top part of bed No. 7, or in the division between that bed 

 and No. 6. At Stanley hill, where the corals are plentiful, they 

 were found either in association with the pyritic crystals, or in a 

 lighter coloured mottled clay, such as would be caused by the 

 weathering down and mixture of beds Nos. 6 and 7. The conclusion 

 at which I arrived, after making examination, was, that they lie 

 chiefly between the two above-mentioned beds, and that they denote 

 a quiet period during the deposition of the transition beds from the 

 Middle to the Upper Lias. This is also the position of the peculiar 

 so-called Montlivaltia which occurs in the transition beds from the 

 Middle to the Upper Lias at Adderbury and Chipping Warden, 

 Oxfordshire, to which I gave the name of Montlivaltia tuberculata. 



Bed No. 8 is, without doubt, the top of the Middle Lias, dif- 



