540 me. l. f. spath on [Dec. 1913, 



25. Ore Jtjeassic Ammonites from Jebel Zaghuan (Tunisia). By 

 Leonard Feank Spath, B.Sc, F.G.S. (Read March 5th, 

 1913.) 



[Plates LII & LIIL] 



Contents. 



Page 



I. Introductory Remarks 540 



II. The Jurassic Rocks of Jebel Zaghuau and their 



Cephalopod .Fauna 541 



III. Description of the Ammonites 547 



I. Inteodtjctoet Bemaeks. 



The fossils described in the following pages were collected on a 

 harried excursion to the mountain of Zaghuan, the graceful, sharp- 

 peaked summit of which is a prominent landmark that greets the 

 eyes of travellers in the Begency of Tunis. Apart from being 

 the most conspicuous mountain in the country — though inferior 

 in absolute height to Jebel Chambi, — Zaghuan also forms the 

 most important elevation of the Tunisian Atlas from a geological 

 point of view, and the tectonic problems which it suggests are 

 manifold and of exceeding interest. "Without discussiug these, it 

 may suffice to mention that the late Dr. Fervinquiere in 1903 * 

 summarized the existing geological knowledge of the mountain as 

 follows : 



'Massive limestones of Liassic age form the principal mass of the mountain, 

 ■whereas the Oxfordian and Tithonian play but a subordinate part in its 

 constitution.' 



As a matter of fact, the 'Oxfordian' fossils of Fervinquiere 

 characterize the zone of Peltoceras transvei'sarium, which corre- 

 sponds approximately with what was at one time called in this 

 country the zone of Aspidoceras perarmatum. On the other hand, 

 he mentions Kimmeridgian forms, but includes them in the 

 Tithonian. 



A later work by the same author 2 is devoted entirely to Tunisian 

 cephalopods. Very few of the ammonites are of Jurassic age, 

 however, and of these only about ten come from Jebel Zaghuan, 

 none from the pre-Corallian deposits. Several other works on the 

 geology of Tunis have been published since ; but, so far as I am 

 aware, no new facts regarding the mountain have come to light. 

 I offer the following notes, therefore, in the hope that they may be 

 of general interest ; for the study of the ammonites has revealed 



1 « Etude Geologique de la Tunisie Centrale ' Paris, 1903, p. 253 : ' Djebel 

 Zaghojian.' 



* ' Etudes de Paleontologie Tunisienne : I — Cephalopodes des Terrains 

 Secondaires ' Text & atlas, Paris, 1907. 



