24 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 22, 



Notes on the Fossils collected by Mr. Geikie from the Lias 

 of the Isles of Pabba, Scalpa, and Skye. Bv Thomas 

 Wright, M.D., F.R.S.E. 



At the request of my friend Professor Ramsay I made an exami- 

 nation of the fossils collected last summer by Mr. Geikie from the 

 Lias of Pabba, Scalpa, and Strath ; first, for the purpose of deter- 

 mining the species to which they belonged ; and, secondly, to assign 

 the subdivisions of the formation which they characterized. 



Previous to laying before the Geological Society my notes on the 

 different species contained in this interesting collection, it is neces- 

 sary that I should premise a few remarks on the classification of the 

 Lias, in order that I may rigorously define the portion of the for- 

 mation I include in the term middle ; so that the true stratigraphical 

 position of the beds which yielded these organisms may be fixed 

 with certainty. 



English authors in general divide the Lias into Upper Lias, Marl- 

 stone, and Lower Lias ; but these subdivisions require additions and 

 modifications in order to place our liassic beds in correlation with 

 those of French and German authors. For on the Upper Lias 

 clays are superimposed beds, which, previously to the publication of 

 my memoir on the "Upper Lias Sands"*, were grouped with the 

 Inferior Oolite ; and with the Lower Lias are placed several beds 

 which, with the Marlstone, constitute the Middle Lias of the Con- 

 tinental authors. 



Taking the Lias-beds as they occur in Gloucestershire, in descend- 

 ing order, and naming each bed by the species of Ammonite which 

 characterizes it, we find the series tabulated at p. 25, which is nearly 

 the equivalent of the Lias-beds of Germany so well described by 

 Dr. Oppel in his valuable work now passing through the press, " Die 

 Jura-Formation, &c." In the following Table (p. 25) a comparative 

 view is exhibited of the subdivisions of the Lias, according to Prof. 

 Quenstedt, Dr. Oppel, the late A. d'Orbigny, and Sir Roderick Mur- 

 chison. 



The following list contains the most characteristic species of Mol- 

 lusca and Radiata of the Middle Lias of Gloucestershire, and is given 

 for the purpose of indicating the age of the Pabba-shales, by a com- 

 parison of the respective fossils. 



Belemnites paxillosus, Schloth. Ammonites Henleyi, Sow. 



elongatus, Miller. ibex, Querist. (Boblayei, d'Orb.) 



clavatus, Schloth. bipunctatus,i?oem. (Valdani,rf'0.) 



compressus, Stahl. Loscombi, Sow. 



longissimus, Miller. - capricornus, Schloth. (maculatus, 



breviformis, Ziet. Y. d$f B.) 



Nautilus intermedius, Sow. Jamesoni, Sow. 



Ammonites spinatus, Brug. Davcei, Sow. 



margaritatus, Montf. Maugenesti, d'Orb. 



Normanianus, d'Orb. Taylori, Sow. 



beterophyllus (amaltheus), Querist. Centaurus, d'Orb. 



fimbriatus, Sow. Chemnitzia undulata, d'Orb. 



[Continued at p. 26. j 



* Quarterly Journal of the Geological Society, vol. xii. p. 292. 



