702 J. W. JUDD ON THE SECONDARY ROCKS OE SCOTLAND. 



Thus in Skye and the adjoining districts we find the Lower-Lias 

 limestones and shales exhibiting a tendency to assume a more sandy 

 character, the former passing in many cases into a calcareous grit, 

 and the latter into an argillaceous sandstone ; while in some places 

 masses of coarse sandstone and quartzose conglomerate make their 

 appearance in the series; and these certainly seem to indicate the 

 proximity of an ancient shore-line. Nowhere, however, do we find 

 proofs of the prevalence of actual estuarine conditions in the midst 

 of the Lower Lias of the Western Highlands in the same manner 

 in which we have shown such to occur among the equivalent 

 deposits in Sutherland. 



The sandstone, grits, and conglomerates intercalated in the Lower 

 Lias series of the Hebrides are usually very unfossiliferous ; they, 

 however, occasionally exhibit some evidences of having been accu- 

 mulated near to land, in the abundant fragments of wood which 

 they contain. The conglomerates are usually made up of well- 

 rounded pebbles of white quartz ; and only few and often obscure 

 casts of shells occur in them ; these, however, enable us to pro- 

 nounce with certainty as to the marine origin of the beds which 

 contain them. 



In the limestones and shales the fossils, of which individuals are 

 particularly abundant in the Lower Lias of the Western Highlands, 

 serve clearly to indicate the position of the several beds in the 

 geological series. Although, however, individual fossils are so ex- 

 ceedingly abundant, the number of species which can be recorded is 

 by no means so great as would be at first sight anticipated ; they 

 are nevertheless amply sufficient for defining the geological horizons 

 of the beds in which they occur. 



The great mass of the strata in question clearly belongs to the 

 " Lima-he&s or Zone of Ammonites BucJclandi." This is proved by 

 the remarkable abundance of Gryphcm arcuata of the typical form, 

 and by the numerous and fine examples of Lima gigantea which occur 

 — and especially by the prevalence of such characteristic arietiform 

 Ammonites as A. BucJclandi, Sow., A. Conybeari, Sow., A. Kridion, 

 Hehl, and many others. Many other fossils which occur with 

 these, such as Nautilus striatus, Sow., Pinna Hartmanni, Defr., Lima 

 succincta, Schloth., and L. pectinoides, Sow., Spiriferina verrucosa, 

 v. Buch, S. Walcotti, Sow., serve to confirm the correctness of the 

 identification of these beds with the well-known deposits of England, 

 Burgundy, and Wiirttemberg. 



- I have in another work* pointed out the fact that in Lincolnshire 

 the upper part of the BucJdandi-be&s presents some peculiarities in 

 its fauna which are well worthy of notice and that the deposits on 

 this horizon in that county, which have now become so well known 

 on account of the thick masses of valuable ironstone which they 

 contain, clearly represent that subzone to which Dr. Oppel applied 

 the name of zone of Ammonites geometricus, Phill. (an Ammonite 

 which is now regarded as identical with A. semicostatus, Y. & B.). 



* Memoirs of the Geological Survey of England and Wales— " The Geology 

 of Kutlancl," &c. pp. 42-45. 



