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 GEOLOGY and it was cut through at the northern end of Catesby tunnel on the G. C. Railway. The Middle Lias A considerable change in the nature of the deposits, without any striking change in the general assemblage of fossils, occurs as we pass upwards into the Middle from the Lower Lias. It would appear that the general depression had ceased, that the north-westerly uplift previously referred to had commenced, and that it included or came near to western and north-western Northamptonshire, for in these directions we find such deposits in the Middle Lias as would be likely to result from the disturb- ance and redistribution of the Lower Lias near at hand, such as pebble beds containing rolled Lower Lias fossils {A. capricornus for instance), sandstones, limestones, marls, and especially thick clay beds with a much larger percentage of the quickly settling sand and mica than the Lower Lias beds contain. It is only in the western parts of the county that the Middle Lias has been and can be fully investigated, hence the abbreviated type section is taken from there.' TYPICAL SECTION OF THE MIDDLE LIAS OF NORTHAMPTONSHIRE Name of Bed or Zone Description of the Beds Approximate thickness Transition Bed or ' Acutus ' Zone A. Soft grey marl, or stone, passing upwards into red sandy clay, with Ammonites acutus ft. in. 6 'Spinatus' Zone many fossils. Ammonites spinatus (rare) 2. Calcareous or sandy clay, may have ferruginous nodules and one or more beds of sandy limestone 6 9 'Margaritatus' Zone (upper) 3. Two beds of soft sandstone, or shale, highly fossiliferous, separated by sandy, micaceous marl or clay ; all containing Ammonites margaritatus 4. Sandy, micaceous and ferruginous clay ; fossils all casts colour, or composed of comminuted shell ; generally contains pebbles and water-worn fragments of fossils 12 12 2 ' Margaritatus ' Zone (lower) or 'Nitesccns'Zone 6. Bluish-grey, sandy, highly micaceous clay, with numerous more calcareous indurated masses and impersistent beds, with Ammonites nitescens, etc. 56 Junction Bed 7. Layer of water-worn nodules, discoloured, bored, in matrix of green sand with numerous foraminifera, oysters and pectens, etc. Resting on ' Capricornus ' zone 6 98 • Beeby Thompson, ' Excursion to the New Railway at Catesby, Northamptonshire,' Proc. Geo/. Assoc, vol. xiv. pt. lO (Nov. 1896), pp. 65-88 ; The Middle Lias of Northamp- tonshire. II
 * I. Rock-bed. A calcareous or sandy bed, often ferruginous,
 * 5. Hard mottled rock, may be largely oolitic, and green in
 * Water-bearing.