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THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
reddish-brown on exposure. This lower portion sometimes 
passes into a hard and compact limestone, but even then, 
apart from the fossils it contains, it is easily identified. 
The thickness of the bed seldom exceeds six inches, but 
near to Northampton it reaches fourteen inches. 
Considering the thinness of the bed, the number of 
distinct genera and species of fossils is very large. The 
characteristic ammonite, A. acntus (Tate), is nearly every¬ 
where abundant, and yasteropods must have swarmed in the 
shallow sea in which it was deposited. Most of the fossils of 
the “ Spinatus ” Zone are found in this bed, hence it is usually 
included in the Middle Lias. Rhynchonellce , Ammonites , and 
Belernnites are common, but they are all small, as though the 
conditions were unsuitable to their proper development. 
Serpuke are rather abundant, and of large size. 
The list of fossils given below is by no means a complete 
one, but only a list of such as can be found in most places, 
where the bed is developed, and since these places are rather 
numerous I have omitted giving the localities from which the 
fossils have been obtained, as in the case of the rock-bed. 
Fossils :— 
Pecten textorius. 
Pecten ccquiralvis . 
Pecten liasinus. 
Cucullcea Mimsteri. 
Astarte Voltzii. 
Astarte stria to-silica ta. 
Cardinia p kite a. 
Ceromya (Venus) bombax. 
Pihynchonella tetrahedra . 
Rhynchonella tetrahedra , var. 
Northamptonensis. 
Ditrypa etalensis. 
Ditrypa circinata. 
A ctceonina 1 Iminsterensis . 
Ammonites acutus. 
A mmo nites Hoi an drei. 
Belernnites. 
Cerithium ferreum. 
Cerithium liassicum. 
Chemnitzia foveolata. 
Chemnitzia semitecta. 
Fluey elm Gaudryanus . 
Phasianella turbinata. 
Turbo linctus. 
Trochus lineatus. 
Cryptcenia consobrina. 
Cryptamia expansa. 
Conditions of Deposit of the Middle Lias. 
That the various members of the Lias—Lower, Middle, 
and Upper—are conformable one with the other is generally 
admitted ; there is no great break in the succession of life at 
any part of the series, although considerable changes occur 
in the nature of the sediment. 
From the lithological characters of the part of the Lias 
we have been considering (ferruyinous limestones and sandy 
clays containiny concretionary ferruyinous nodules) as well as 
