parti] JURASSIC CHRONOLOGY: LIAS. 69 



fairly well-known already; (2) the following sequence given by 

 Mr. Richardson from one locality, Bayliss Hill, near Honeybourne 

 (Worcestershire), which can be epitomized as follows: — 



Bed 1. Bifericeras subplanicosta, 



Polymorph ites polymorphic, 



Microceras densinodum, 

 Bed 2. Microceras densinodum, 

 Bed 3. Echioceras raricostatum, 



Oxynoticeras guibalianwn ; 



(3) the inference to be gathered from Mr. Richardson's remarks 

 about the Toddington cutting, that Bifericeras tiibellum must be 

 high up in pre-bron/ii beds. This finds a certain amount of 

 support from Yorkshire, where Ammonites tubellits is reported 

 as well above the subplanicosta beds. 1 With these details for a 

 guide the accompanying table (I) has been constructed — the 

 different exposures (1-16) running practically in a line from south- 

 west to north-east, approximately along the strike, though rising 

 to pass through a tract of higher ground in the neighbourhood of 

 Dixton, as the diagram reveals. 



(c) Fauna! Notes. 



The following remarks concerning some of the species are a 

 necessary prelude to any consideration of the facts brought out in 

 the Table. 



Oistoceras arcigerens. This is supposed not to be an Oisto- 

 ceras, but a species of Ambh/coceras as interpreted by Dr. A. E. 

 Trueinan, 3 similar to species of the capricornum bed of Pilley, 

 Leckhampton (Gloucestershire), Hwiccian 5, and not to indicate 

 Oistoceras Beds (Hwiccian 9). 



PoLi'MORPHiTES polymorphous. This is an incorrect identifi- 

 cation, for which I am possibly responsible ; at any rate, it echoes 

 a misidentification which I gave many years ago. It is possibly 

 not a JPoli/morphites ; it is certainly not polymorphus, which is a 

 lineate form. This species, if there are not more than one in- 

 volved, is sometimes smooth, sometimes faintly rugose. It has a 

 likeness to Ammonites electre Reynes, 3 A. abnonnis Hauer in 

 Reviles, 4 and to Psiloceras abnorme Hauer in Greyer, 5 which is, 

 however, larger and more rugose. It is also curiously similar to 

 the young Ammonites liartmanni figured by Dumortier, 6 an 

 identification which seems suspicious because of its entire lack of 

 even a nascent carina, and because it does not come from the same 

 locality as the larger examples. 



Microceras hejSSINohum. Here are combined the various 

 forms recorded by Mi'. Richardson under JSlicroceras. They are 



1 II, 6, p. 70. 2 XXI, 1, p. 279. 



3 XVII, pi. xxxiv, figs. 12-15. 4 XVII, pi. xliii, figs. 13 & 14. 



b VIII, pi. ii, figs. 24 & 25. ° VI, pi. xxi, figs. 8 & 9. 



