THE MLDIDE LIAS OF NORTHAMPTONSHIRE. 
277 
than elsewhere. Cardinia Icevis in bed “ F,” and Cardinia 
concinnci in bed “ 13,” are abundant only at Watford, and 
Cardinia crassissima only at Da veil try ; indeed, I have not 
found this latter form elsewhere in the county.* 
The My as, which are exceedingly abundant in beds “ F ” 
and “ H,” are scarcely ever met with in the Spinatus ” 
Zone. Pleuromya costata , chiefly in “ F,” and Pholadoinya 
ambiyua, chiefly in “H,” are the commonest forms. 
Passing on to the Brachiopods ,we notice that although rather 
numerous in species, and exceedingly so in numbers, there is 
only a record of two from the ‘‘ Maryaritatus ” Zone. In North¬ 
amptonshire I have never myself found a single brachiopod 
in beds that I knew to belong to the “ Margaritat-us ” Zone, 
hence the suggestion I made in a previous part of using the 
brachiopods as indicators of the “Spinatus ” Zone. There 
is a section near to Daventry which illustrates this rather 
remarkable phenomenon. A single bed of stone 3ft. or 4ft. 
thick yields in the lower part Gasteropods and large numbers 
of Cardinias, Pectens, Astarte, Cardita, &c., characteristic of 
the ‘ ‘ Margaritatus ” Zone ,but no brachiopods; the upper portion 
contains thousands of Rhynchonella tetrahedra, hut not a single 
specimen of the fossils enumerated above, with the exception 
of the Pectens. 
SerpulcE, it will have been noticed, are well represented in 
the Transition-bed. The ossicles of Pentacrinites are sufficiently 
abundant to constitute thick layers in the Rock-bed at various 
places. 
Corals are decidedly rare ; nearly all of those quoted in 
the list came from the extreme south-western part of the 
county. Thecocyathus tuberculatus has, however, a fairly wide 
range. 
It is interesting to notice that a number of the fossils 
found in the Rock-bed and Transition-bed of Northampton¬ 
shire are met with much lower down in the Lias in other 
localities, and here, too, we should in all probability find them 
if we had better opportunities for examination, whereas they 
are absent in intermediate zones. I might give as illustrations, 
Trochus Thetis, T. Gaudryanus, Pecten textorius, Spiriferiva 
Walcottii, 8. rostrata, Terebratula punctata, dec. The migra¬ 
tion and return of these may perhaps be used to throw more 
light on the physical conditions existing during the periods 
of their exile and return. 
(To be continued.) 
* The section in which this fossil occurs was only exposed recently, 
hence a description of it does not occur in Part I. 
