Peacock : Naturalists at Lincoln. 



the Marlstone Rock bed did not occur at Lincoln, but that the 

 sands and clays passed directly upwards into the Upper Lias. 

 More recently, in a detailed description of the section in Hand- 

 ley's pit by Mr. J. H. Cooke, F.G.S. (Geological Magazine, 

 June 1897), it was asserted that the marlstone did occur at 

 Lincoln, and it was largely that the members might have an 

 opportunity of judging on these two opposite opinions that this 

 excursion had been made. One of the commonest type fossils 

 of the marlstone is the brachiopod shell Rhynchonella tetrahedra, 

 which often occurs in great masses, forming the rock itself. In 

 Handler's pit there occurs a band of limestone about two feet 

 thick which Mr. Cooke identified as the marlstone. This 

 identification depended upon the fragment of one shell which 

 appeared to him as Rhynchonella tetrahedra. This limestone 

 band was carefully examined, but none were fortunate enough 

 to find any trace of the type fossil, and, lithologically, the band 

 appeared very different in character to the marlstone which 

 occurs both north and south of Lincoln. Furthermore, the 

 clays which overlie this band contain some of the commonest 

 and most easily identified fossils of the lower division of the 

 Middle Lias, and Ammonites margaritatus occurs in its most 

 regular form both in the band and for at least seven feet above 

 it. In most other parts of the county the top surface of the 

 marlstone is taken as the upper limit of the Middle Lias, and 

 the clays which occur immediately above it are placed in the 

 Upper Lias. Also, where the junction is well seen it is generally 

 found that a certain amount of erosion has taken place before 

 the deposit of the Upper Lias has commenced. These facts 

 seem to demonstrate that this limestone band is only a more 

 highly-developed example of the numerous other bands in the 

 Middle Lias clays ; that the clays lying immediately above it 

 belong still to the lower division of the Middle Lias, and that 

 sufficient proof is not yet forthcoming to show that the marl- 

 stone does occur in the Lincoln Lias. 



Numerous fossils were collected from the Middle Lias in 

 Handler's pit, and from some broken nodules found in the 

 lowest portion of the pit Ammonites capricornus was obtained ,* 

 so that it was thought possible that the lower limit of the 

 Middle Lias was reached, and the Lower Lias appearing, but as 

 the division is a palaeontological one, and as capricornus some- 

 times occurs out of place in the Lincolnshire Lias, it will be 

 necessary to prove the absence of margaritatus (an undisputed 

 Middle Lias species) before the definite thickness of the Middle 



Naturalist. 



