52 DE. W. D. LAIS'G OX THE STRATIGRAPHY [vol. lxxix,. 



of which to M. hirchi he is (I understand) not absolutely deter- 

 mined, appear to represent the upper Arietite fauna. 1 



What are probably other important stratigraphical results em- 

 bodied in the present paper are (1) the unexpected position of' 

 A. hrooki~; (2) the recognition of one distinct Amioceras horizon 

 at the base, and another at some 20 feet from the top of the 

 series ; (3) the presence of a very low Jiiplieroceras ; (4) the 

 discover} 7 (due to Dr. Spath) of the horizon of ammonites of the 

 A.-plotti group ; (5) the appearance of a Sulciferit'es [Spath] 

 fauna at the lower Arietite horizon ; (6) the finding of a new 

 genus, Paramioceras [Spath], containing many species, some 

 new, and confined to the inch-thick bed 70 c; and (7) the dis- 

 covery of an abundant Agassiceras fauna below the Paramio- 

 ceras horizon. 



My thanks are due to Mr. Eobert Clark, of Lyme, who showed 

 me the brooki-horizon ; to Dr. L. F. Spath, who contributes 

 Part II of this paper, for much help with the ammonites ; to 

 Mr. J. W. Tutcher for kindly lending me ammonites from the 

 Bath-Rad stock area, for comparison with the Charmouth forms • 

 to Dr. A. E. Trueman for identifying some of the lamellibranchs ; 

 to Mr. W. A. Richardson (who contributes Part III) and to 

 Mr. "W. Campbell Smith, M.C., for help with the rocks and 

 minerals ; to Mr. A. Reeley for help in the field ; lastly, to my 

 wife, for constant help in the field and encouragement at home. 



(B) Nomenclature of Rock-Forms. 



Before considering in detail the Shales- with-Beef, it is desirable 

 to explain the terms used in describing the rock-forms. 



(1) Beef. — Fibrous calcium carbonate, always showing cone- 

 in-cone structure, even if only on a microscopic scale. Seams of" 

 all thicknesses occur, from about 1/16 inch to some 4 inches. 

 Generally speaking, the thicker the seam, the more obvious is. 

 the cone-in-cone structure ; but it is possible to note conspicuous 

 cone-in-cone structure in a very thin seam. Seams exceeding 

 2 inches in thickness, however, always show cone-in-cone structure 

 clearly. All seams are double, and the cones of each layer inter- 

 penetrate at the junction. Naturally, such layers do not readily 

 separate. Sometimes, however, one layer is very thin and, appa- 

 rently, may temporarily thin out altogether. Further, such two- 



1 At my request, Mr. Tutcher very kindly sent to Dr. Spath these specimens 

 for examination, as well as much Agassiceras material. Thanks to his prompt 

 help, we have been able to compare the Dorset with the Bath-Radstock 

 specimens. 



2 This is given in an addendum- and corrigendum- slip to Dr. A. Morley 

 Davies's ' Introduction to Palaeontology ' 1920. On discovering the Broolci- 

 Bed, I urged Dr. Davies to correct on the first opportunity the position of 

 A. brooki as hitherto supposed and as given in his text-book ; and this he did 

 as just stated. The exact position of the bed, however, and of the neigh- 

 bouring sequence is here given for the first time. 



