268 MR. s. s. BUCKMAJf OX [vol. Ixxiii, 



fig. B, p. 272). As a consequence it may be expected that the 

 faunal sequence in early Raasayan was more compKcated than 

 that shown in Table V. The Sodbury evidence . gives the asso- 

 ciation of ' Am. aff. armatus ' and ' A. raricostatus ' [an armatoid 

 and an Ecliiocei^as'] below the densiiiodus \ob8oletum?'\ horizon. 

 The Midlands, according to Mr. Thompson's evidence, show the 

 second at a lower horizon than various armatoids which he asso- 

 ciates with Am. suhplanicosta. Cheltenham has a very definite 

 sithplanicosta horizon, and it is below this that various armatoids 

 occur. \ consideration of these points suggests that, instead of 

 the two horizons of the Table, there may be three if not four in 

 the following descending order : — 



(d) suhplanicosta. 



(c) ohsoletmn (densinodvm). 



(b) armatoids. 



(a) Echiocerates. 



Attention to this point would be desirable. Ammonites are 

 abundant, but small. The}^ Have not yet been examined in a 

 sufficiently critical manner — a very long task ; in many cases their 

 identification with alread}" named species is open to much doubt. 



The faunal repetition in the Raasayan begins to make many 

 things clearer. For instance, it is now ]30ssible to understand the 

 absence of large armati from the Midlands ; and the very remark- 

 able number of species of Ecliioceras. The list in 'Yorkshire Type 

 Ammonites ' (p. 96 c, 1914) enumerates 44 species, and is by no 

 means exhaustive. As the product of development at intervals 

 during a very long period of time, the}^ are much more under- 

 standable than as the product of one date ; and, as the outcome of 

 repetitive series evolving on parallel lines, the frequent similarity 

 but not identity in the Echiocerata is explicable. 



V. SiXEMUEIAX. 



The Scottish deposits are not rich in Ammonites ; but there is 

 evidence for the sequence of certain faunas, while loose blocks 

 on the Hallaig shore of Raasay indicate the presence of others. 

 The evidence is instructive when compared with that of English 

 localities, especially with the detailed work done by Mr. Lang on 

 the Dorset Coast. 



The great increase which the Scottish deposits have proved in 

 the faunal phases of the Raasayan might have been anticipated 

 from other localities, if strict attention had been paid to dissimilar 

 faunas. Now, in the Sinemurian, the case may, perhaps, be 

 reversed : by parang attention to faunal dissimilarities it is hoped 

 to anticipate that full faunal sequence which may some day be 

 proved in a thick deposit. 



With increase of horizons the need for division of the Sine- 

 murian seems to be great. It has been felt already. Choffat has 

 divided it into Upper, Middle, and Lower Sinemurian,^ and this 



^ ' L'Infralias & le Sinemurien du Portugul ' Comm. Serv. Geol. Port, v 

 (1903) pp. 54-106. 



