Meports & Proceedings — Geological Society of London. 233 



Moreover, the ammonites collected by the author afford sufficient 

 evidence of the presence of the zone of Reinechia miceps, which occurs 

 in Algeria, but had been supposed absent in Tunis together with the 

 other beds intervening between the Middle Lias and the Corallian. 

 The Middle Jurassic transgression must, therefore, have begun in 

 Lower Oxfordian times, since the deposits of that age probably rest 

 directly on the Domerian. 



The upper zones of the Oxfordian, as well as the lower part of the 

 Corallian as interpreted by Mr. Buckman — that is, the cordatus and 

 •pre-cordatus zones — seem to be absent, although there is a possibility 

 that they have been cut out by the extensive faulting, of which the 

 general calamitization seems to afford proof. 



On the other hand, the Argovian, or zone of Peltoceras trans- 

 versarium, is very well represented. About seventy specimens were 

 collected at a locality called Sidi Bu Gubrm, but the list includes 

 forms from the transversarius zone mixed with some from the 

 ' acanthicus ' beds. If we call to mind the curious fact that not only 

 in the Southern Alps but also in Sicily the Argovian is very well 

 developed, to the exclusion of the higher beds of the Corallian, 

 followed without any apparent break by the ' acafitMcus ' beds, it 

 appears quite probable that the two ' zones ' occur here in a similar 

 mauner, and that the apparent mixture is not due to doubtful 

 identifications of badly preserved specimens. 



Most of the forms are certainly of Argovian age, and with regard 

 to the remainder the stratigraphical value is problematical. The 

 presence of the ' acanthicus zone ', therefore, must remain doubtful, 

 although on the neighbouring Jebel Ben Sai'dan deposits of that age 

 occur, and indicate a third transgression in Central Tunis during 

 Kimmeridgian times, which brought back the sea and gave rise to 

 deposits of red ammonitic Knollenkalk exactly similar to that of the 

 Lower Oxfordian and the Argovian. 



(ii) March 19, 1913. — Dr. Aubrey Strahan, F.R.S., President, 



in the Chair. 



The President announced that the Council had awarded the 

 Proceeds of the Daniel Pidgeon Fund for the present year to Boderick 

 Urwick Sayce, B.A., University College of Wales, Aberystwyth, who 

 proposes to investigate the rock-succession and structure of the 

 Ystwyth Yalley and its neighbourhood. 



The following communications were read : — 



1. "The Geology of J^orthern Peru: Tertiary and Quaternary 

 Beds." By Beeby Thompson, P.G.S., P.C.S. 



Tliis paper deals with the physiography, physical history, and 

 geology of some 600 square miles of territory in the westernmost 

 part of South America, between the fourth and fifth degrees of south 

 latitude, and between the Andes and the sea. 



The connexion between the surface configuration of the district 

 and the arid nature of the climate is shown. 



A description is given of the tablazos, raised beaches, quebradas, 

 and Salinas, etc. 



