J. W. JUDD ON THE SECONDARY ROCKS OF SCOTLAND. 703 



Precisely the same observation holds good with respect to the Lower 

 Lias strata of the Western Highlands. Here, as in Lincolnshire, we 

 find that the upper part of the " -Lima-beds," which exhibits some 

 peculiarity in its mineral characters, can also be separated by the 

 presence of certain interesting and well-marked forms of Ammonites 

 and other shells from the great mass of strata below. 



It seems to me that this partial change of fauna is by no means 

 unworthy of record in the description which I propose to give of 

 the Lower Lias of Scotland. The changes in the characters of the 

 Ammonites which characterize this upper portion of the " Lima- 

 beds " is especially remarkable and significant ; and what is most 

 important of all is, that precisely parallel changes can be traced as 

 making their appearance at the same point in the geological series 

 in Scotland, the North of England, and in Swabia. Thus, while the 

 Ammonite forms (I hesitate to call them species) so abundant in 

 the Lower Zone (Zone of Ammonites Bucklandi) disappear, a new 

 group of forms, with a most unmistakable family resemblance, takes 

 their place in the Upper Zone (Zone of Ammonites semicostatus). 

 Some of these forms, which are distinguished by certain well-marked 

 characters which they have in common, have been already figured 

 and described by Quenstedt ; and I hope that a complete series of 

 them, selected from the rich cabinets of the Rev. J. E. Cross, of 

 Appleby, who has done so much towards working out the fine fauna 

 of the Scunthorpe and Froddingham ironstones, will soon be ren- 

 dered familiar to geologists by the monograph of Dr. Wright now 

 in course of preparation. In the Western Islands we find a number 

 of other minute peculiarities in the fauna of the Upper Zone of the 

 Lima-beds, such as we also found in Lincolnshire ; in both localities 

 some new forms of Mollusca occur, others disappear, while others 

 again exhibit distinct and characteristic varietal features : thus in 

 both localities Lima gigantea assumes a size which it is never known 

 to attain in the Lower beds ; and this increased size is accompanied 

 by peculiarities of form and surface-sculpture which are by no 

 means unworthy of notice and study. 



While, however, the inferior division of the Lower Lias (that to 

 which Quenstedt applies the term Lias a) is so admirably developed 

 in the Western Highlands, its upper member (Lias /3 of Quenstedt) 

 appears to be wholly, or almost wholly, unrepresented in the area. In 

 Eaasay the dark shales containing the fossils of the zones of Ammo- 

 nites armatus and A. Jamesoni, constituting the base of the Middle 

 Lias (Lias y of Quenstedt), are seen resting directly upon the 

 semicostatus-\>e&s. Only in the northern part of the Mull have I 

 succeeded in detecting any trace of the fauna of the Lias /3 in the 

 Western Highlands. At Tobermory a very fossiliferous stratum 

 occurs (as noticed by Hugh Miller), the palseontological characters 

 of which seem to be of considerable interest, from the fact that in 

 it forms seem to be mingled together which elsewhere characterize 

 the distinct zones of Ammonites ibex, A. Jamesoni, A. armatus, and A. 

 oxynotus. The species, however, are for the most part more or less 

 dwarfed in size in this stratum ; and as there is no clear section 



Q.J.G. S. No. 135. 3 a 



