THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
149 
D. —Soft sandy limestone, often slialy in character, 
abounding in fossils, the most common being 
Pecten liasinus, Protocardiiun truncatum, Astarte , 
q n 
E. —Sandy or marly clay ... ... 2Jft. to 8 0 
“ Margaritatus ” Zone. 
F. —Soft sandy and ferruginous limestone, generally 
slialy; very fossiliferous. The following rather 
abundant :—Ammonites margaritatus, Protocar- 
dium truncatum, Plwladomya ambigua, Pleu- 
romga costata ... ... ... ... ... 3 0 
(i.—Sandy marl or clay, micaceous and ferruginous; 
Ammonites margaritatus, dc. ... ... ... 6 0 
H. —Soft sandy limestone, abounding in fossils, very 
ferruginous, containing Ammonites margaritatus, 
Pholadomya ambigua, Protocardium truncatum, 
Avicula inccquivalvis, Modiola, dc. ... ... 3 0 
I. —Sandy micaceous clay, very soft and friable ... 4 0 
J. —Micaceous and calcareous sandstone ; Protocar¬ 
dium truncatum, Pecten liasinus, Fucoul markings, 
all abundant ... ... ... ... ... 2 6 
K. —Sandy, micaceous, and ferruginous shale or clay, 
abounding in fossils, mostly casts: —Protocardium 
truncatum, Avicula, Pectens, Modiola, dc. .. 5 6 
L. —A mottled, yellow and green, shelly limestone, 
sometimes very hard, containing many well 
preserved fossils; large specimens of Pecten 
liasinus rather characteristic ... ... ... 2 0 
Springs commonly met with. 
“ Capricornus ” Zone. 
Dark blue clay. 
1 have found this typical section a very useful aid in 
the study of the Middle Lias of Northamptonshire, and 
although constructed three or four years ago with consider¬ 
able diffidence, I have seen no reason for altering it materially 
since. It must be borne in mind, however, that the Middle 
Lias of Northamptonshire, like that of most districts, is a 
very variable formation, and so the section may be approxi¬ 
mate only in any particular place, but certainly all the beds 
described do exist, as the numerous sections 1 shall give will 
show, and I think there are no others that it does not include. 
The variations that may be expected are these :—(1) An 
absence of some of the beds altogether, and this, perhaps, 
more often at the junction of the “ spinatus” and “margari¬ 
tatus” zones than elsewhere. (2) A coalescence of two or 
