part 4] JURASSIC cheonology. 435 



Hemeree. Fauna and JLocalities. 



scissum. Sredi/la spp. 



\_Ancolioceraslopaliniforme]. Burton Bradstock (Dorset) ; Cotteswolds (Gloucester- 



sliirft) in the Sandy Ferruginous Limestone; 



Normandy ; Rhone Basin ? 



Hammatoceras {insigne). Watton Cliff, Eype (Dorset), Junction-Bed; Cole 



\_Dumortierialdispansum']. (Somerset), Bruton Sands ; Cotteswolds, Cepha- 



lopod_Bed ; widespread on the Continent. 



VI. A Pal.eontological Note — Tetrarhynchia 



7H0RNC0MBJENSIS, 110111. nOV. 



J. F. Walker identified specimens of this characteristic fossil 

 from the Thorncombe hed as his JRliynclioneUa nortliamptonensis, 

 and it is presumably the same form from the same deposit at 

 North Allington, near Bridport, that he called ^ Mhynchonella 

 tetraliedra^ var. nortliainptonensis.'' ^ But the Thorncombe form 

 certainly is not the same species as that from Northampton shire, ^ 

 for that has clean-cut, sharp ribs ; whereas the Thorncombe fossil 

 has blunt, somewhat rounded-off ribs, and has a general smoothed- 

 ofE appearance. As the two forms are certainly not contemjDoraries, 

 as the Thorncombe fossil marks a particularly distinctive horizon 

 on the Dorset coast, and as it has been frequently necessary to cite 

 the name, it seems preferable to give it a distinct appellation rather 

 than to perpetuate one which will require changing. I have 

 selected a type to be figured in the proposed palaeontological 

 sequel to this paper, where it is also hoped to figure and describe 

 various ammonites and brachiopods, which have special bearing on 

 the chronology of Lias-Oolite rocks as well as giving evidence for 

 widespread dejDOsition of certain deposits. 



VII. BiBLIOCIEAPHT. 



I, 1. BucKMAN, S. S. ' The Descent of Soiminia & Hammatoceras'' Q, J.G. S. 

 vol. xlv (1889) p. 651. 



2. Do. 'On the So-called "Upper-Lias Clay" of Down Cliffs' Q.J.G. S. 



vol. xlvi (1890) p. 518. 



3. Do. 'The Bajocian of the Sherborne District: its Relation to Subjacent 



& Superjacent Strata ' Q. J. G. S. vol. xlix (1893) p. 479. 



4. Do. ' Plomoeomorphj- among Jurassic Brachiopoda ' Proc. Cotteswold 



Nat. Field-Club, vol. xiii. pt. 4 (1901) p. 231. 



5. Do. ' Certain Jurassic (Lias-Oolite) Strata of South Dorset, & their 



Correlation ' Q. J. G. S. vol. Ixvi (1910) p. 52. 



6. Do. ' The Brachiopoda of the Namyau Beds, Northern Shan States 



(Burma) ' Palaeontologia Indica, n. s. vol. iii. No. 2, 1917. 



7. Do. 'Jurassic Chronology: I— Lias ' Q. J. G. S. vol. Ixxiii (1917-18) 



p. 257. 



8. Do. 'Type-Ammonites' in & IV, 1919-22. 



9. Do. ' Jurassic Chronology : I — Lias : Supplement 1, West England 



Strata ' Q. J. G. S. vol. Ixxvi (1920) p. 62. 

 II. Davidson, Thomas. 'Monograph of the British Fossil Brachiopoda' 

 (Pal. Soc.) iv, pt. ii, no. 1, Suppl. to the Jurassic & Triassic Species, 

 1876; no. 2, 1878: Appendix to Suppl., 1884. 



^ XII, p. 438. 



^ II, 1878, p. 199, Suppl. pi. xxix, figs. 7-12 : fig. 7 may be taken as lecto- 

 type of the species. 



