ZONE OP AEGOCERAS JAMESONI. 7& 



gives the following section in the lower half of the Middle Lias, " in clem ' Kief und am 

 Abhange cles Berges" in descending order : 1st, J eg.- Centaur us-heA?, ; 2nd, Aeg.- 

 6revispina-heds ; 3rd, Jeg.-armalum-heds. In the first are found Lytoceras fimhriatum 

 and Aegoceras striatum, in the second Aeg. Jamesoni and Aeg. brevispina, and in the 

 third Aeg. armatum and Terebratula subovoides^=-T. punctata. 



In South-west Germany, at the foot of the Swabian Alps, the marls of the Middle 

 Lias are seen resting upon Lower Lias clays cowidimmg Arietites raricostatus. In these, 

 the Numismalis-marls of Quenstedt, are found Gryphcea obliqua and Belemnites elongatus, 

 which now appear for the first time, Belemnites acictus, so common in the older beds, 

 being absent. Pecten priscus, Lima Hermanni, and other bivalved shells, as Pholadomya 

 decorata, are likewise found with Bhynchonella tetraedra, Rliyn. calcicosta, and Spiriferina 

 M'iinsteri. Above these forerunners of the new Fauna are large Ammonites, embedded in 

 a calcareous matrix, representing varieties of Aegoceras armatum ; and in marls still 

 higher in the sections Aegoceras Jamesoni appears for the first time associated with 

 Aegoceras brevispina, Aegoceras Taylori, Harpoceras Masseanum, and Harpoceras 

 arietiforme. Associated with the Cephalopods are Brachiopods, represented by Wald- 

 heimia numismalis, RhyncJionella rimosa, Rhynclionella variabilis, also Bentacrinus 

 basaltiformis, with many Mollusca, which represent the zone of Aegoceras Jamesoni in 

 Wiirttemberg. It is important to note the very great change that takes place in 

 the life of the Molluscan Fauna with the dawn of the Middle Lias, and to observe the 

 great contrast between the palaeontology of the Jamesoni, Ibex, and Henleyi zones, 

 when compared with those we have studied in examining the various successive horizons 

 of life in the Lower Lias. 



In France the Ja7nesoni-hQA& are well developed in several Departments. In 

 Normandy they would appear to be included by Prof. Deslongchamps^ in the " Calcaires 

 et Marnes a Terebratula numismalis." Although not described as marking a distinct 

 zone, i\iQ Aeg. Jamesoni ■=.Regnardi, d'Orb., has been collected at Evrecy, Calvados. In 

 the Cote d'Or the Jamesoni-beds are described by M. CoUenot," who divides the 

 Middle Lias near Semur into four zones, designating each by a characteristic species of 

 Ammonite, and in descending order he gives the following : 



Zone of Aeg. Henleyi, Sow. 

 „ Aeg. Davoei, Sow. 

 „ Aeg. Ve7iarense, Oj)p. 

 „ Aeg. Valdani, d'Orb. 



In the Valdani-h^d% Aegoceras Jamesoni is found. 



^ Deslongchamps, 'Etudes Jurassique Inf. dela Normandie,' p. 42, 1864. 

 ~ 'Descripliou Gdologique de I'Auxois,' p. 260, 1873. 



