SUPPLEMENT.— LILLIA. 



xv 



History — The A. Lilli of Dumortier differs from the A. Lilli, Hauer, in being 

 less umbilicate, more numerously costate, less tuberculate, and having more 

 elliptical whorls. It therefore requires a new name. 



A rough fragment found by Mr. B. Thompson, F.G.S., was sent to me a few 

 years ago for identification. I pointed out that it agreed with the A. Lilli, 

 Dumortier (non Hauer), and Mr. Thompson quoted it on my authority in his 

 paper on "The Jurensis -zone in Northamptonshire" ('Journal Northants N. H. 

 Soc.,' 1890). The fragment, however, is not good enough to found a species 

 upon. Therefore Dumortier's figure is taken as the type of Lillia narbonensis ; 

 and this specimen is considered to agree with Dumortier's figure. His drawing 

 represents the rursicostate character as more marked than in the present frag- 

 ment ; but the representation of this character is not uniform, and it has perhaps 

 been exaggerated in places. Also difference in age may have something to do 

 with it. 



Distinction. — The more numerous costas sufficiently separate this species from 

 Lillia Lilli. 



Locality and Stratum. — Northamptonshire : Moulton (Upper Leda-ovum-beds, 1 

 " Upper Lias "), Mr. B. Thompson, F.G.S. 



Date of Existence. — Lilli hemera. 



1 Mr. Thompson claims " the Upper Leda-ovum-beds " as Jurensis zone, and " that [they were] 

 laid down contemporaneously with the sands and Jurensis beds of Gloucestershire and other 

 counties " * (' Northants N. H. Soc.,' 1890, p. 99) ; also that they were deposited later than the 

 " communis -beds." The last point may be admitted without allowing that the strata belong to the 

 Jurense-zone. The fault really lies with the zonal system of nomenclature. With the hemeral 

 system of geological chronology it may be stated that the Upper Leda-ovum-beds were deposited 

 during the hemera Lilli, and before the hemera variabilis, the strata of which are usually taken as the 

 first portion of the Jurense-zoue. So these beds are contemporaneous only with the lower part of the 

 Cotteswold Sands, the portion deposited before Hauqia jugosa appeared. 



* One remark of Mr. Thompson it is necessary to note because it states a fallacy which has led more 

 than anything else to confusion in the matter of palaeontological horizons. " A considerable change 

 in the character of the sediment took place in the west and south-west long before it did with us in 

 Northamptonshire, and this was necessarily accompanied by a change in the fauna generally, and 

 particularly in the Ammonites, which latter seemed less able or willing to accommodate themselves 

 to new conditions than lower forms " (p. 99). It is a great mistake to suppose that Ammonites were 

 influenced by the character of the deposit, though this error has been so widely taught that nearly 

 every writer, myself included, has argued as if it were a fact. When Dorset, Somerset, and 

 Gloucestershire are compared, it will be found that the same species lived when the deposit was 

 argillaceous, arenaceous, or calcareous, and flourished equally well. Notably is this the case when 

 the Middle Lias of Dorset and of Somerset are compared ; or the Lias-Ooiite deposits of Dorset, 

 Somerset, and Gloucestershire, and these again with the Continent. Further, that the Ammonite 



