part 1] Jurassic chkoisology : lias. 81 



is quite impossible, but may be explicable as a treasure lost from 

 some geologist's bag on his road home, 1 obviously came from the 

 same place as A. fowleri, and might almost be a part of that 

 specimen's nodule: it shows many small Sclil 'otliei mice. 



Now, on the fact of this association of Schlotheimia and 

 A. fowleri, the presence of small Sclilotheiniics was regarded as 

 evidence on which to record a denoted us fauna. But Mr. Richardson 

 makes no mention at all of any such ammonite — neither fowleri, 

 denotatus, nor any Arietites. The ammonites that he records 

 with the Sclilotheimice are : — 



(11) Polymorphites polymorphus, 



(8) Gymbites globosus, 



(7) Deroceras bispinatum Hug (armatoid), 



(4) Cheltonia accipitris, 



(3) Oxynoticeras oxynotum, 



with Gymbites cf. personatum Simpson, which may be placed 

 with 8 : it is presumably a development of C. ylobosum and 

 a heteroehronous homceomorph of Ammonites personalis, which is 

 a dwarf Ayassiceras x : that belongs to a much lower horizon 

 (Lymian t5).- 



I have numbered these records to correspond with those in Table I, 

 facing p. 70, so that it will be seen that there are missing any 

 representatives of the subplanicosia and densinodus faunas 

 (10, 9) — also of the 1st Echioceras- Gleviceras fauna (6, 5). These 

 appear to indicate stratal failures (non-sequences) in the Gloucester 

 deposit. Dispersal failure can with difficulty be put forward to 

 account for the absence of the subplanicosta-densinodus fauna 

 over an area of a few square miles or less. For, not only is this 

 fauna fairly widespread — from Wurtemberg to the Hebrides, but 

 it is in good evidence at Cheltenham, about 8 miles to the north- 

 east, and at Standish near Stonehouse (Gloucestershire), about the 

 same distance to the south of the locality under consideration. 

 But, if dispersal failure could not be called in to account for such a 

 purely local absence, stratal failure could justly be assigned : for 

 such failure in quite short distances — even in a few yards — has 

 been proved often enough. 



However, in the present case another cause seems to give a better 

 explanation — nomenclature failure : that the Polymorphites poly- 

 morphus is not the same species as that found in the railway- 

 cuttings, but is the same species as that quoted by Mr. Beeby 

 Thompson from the Oxynotum zone of Warwickshire. 3 This 

 species is, in part, at any rate (for he kindly gave me examples), the 

 Ammonites elect re Beynes, one of those phylogenetically immature 

 species whose generic position is doubtful, because it has not arrived 

 at the stage of developing any special characteristics. But the 



1 Ejecta from geologists' bags, sometimes accidental, sometimes on purpose 

 to lighten a load, have been traced before now as the actual cause of strange 

 and geologically very incorrect records. 



2 See later, p. 91. :i XX, 2, p. 71. 



Q. J. G. S. No. 301. g 



