ATLANTIC REGION 579 



which has been regarded as representative of the Tremadoc, and is, in 

 any case, a continental formation. Above this lies the Armorican grit 

 proper or the "gres du Toulinquet" with intercalated shaly beds. This 

 series contains fossiliferous members, some of them truly marine and 

 others of shore or possibly supra-marine types. Among the latter are 

 numerous trails and other markings generally preserved in relief, such as 

 Tigillites dujrenoyi, Cruziana furcifera, C. prevosti, C. bagnolensis, Vexil- 

 lum sp., Dmdalus, Lumbricaria, etcetera, while the former include many 

 species of Lingula (L. lesueri, L. salteri, L. liawl'ei, 17 etcetera) and 

 Dinobolus bimonti. It further contains the pelecypods Lyrodesma armor- 

 icana, Modiolopsis caillandi, Ctenodonta costce, Nuculcma incola, and 

 Actinodonia cuneaia, while the trilobites are represented by Ogygia ar- 

 moricana. The horizon here indicated is probably Lower or early Middle 

 Arenig. The Armorican sandstone is disconformably succeeded by the 

 "Schistes d' Angers." These comprise, accordang to Kerforne, the fol- 

 lowing divisions, in descending order : 



6. Eaguenez shales. Black shales with Acaste proceva and Synho- 



malonotus arago (a fauna originally described from Spain by 



Verneuil and Barrande). 

 5. Kerarmob. shales. Black shales with Trinucleus bureaui. 

 4. Morgat shales with Ploxoparia tourncminei, Asaplms glabratus, 



Acaste phiUipsi (a fauna originally described by Sharpe from 



Portugal). 

 3. Kerarvail sandstone. 

 2. Sion shales with Synhomalonotus tristani, Asaphus guettardi, 



Calyx murchisoni. This is also the horizon of Didymograptus 



geminiformis. 

 1. Bed oe oolitic iron ore. 



Diseonformity. 

 Armorican grit. 



The fauna of these shales suggests early or Middle Llandeilo, corre- 

 sponding approximately to Dd y of the Bohemian series. The Angers 

 shales are succeeded by the Saint Germain sur Ille sandstone, which 

 Barrois correlates with the G-lenkiln beds of Scotland. It is a shaly 

 micaceous sandstone containing Diplograptidse, Synhomalonotus arago, 

 Acaste incerta, and Trinucleus. The highest Ordovicic division of Brit- 

 tany is the Bosan limestone with a Caradoc fauna, including Orthis 

 actonim, Triplesia spiriferoides, and Trinucleus. 



17 This species is reported by Van Ingen from oolitic hematite at the top of his Bell 

 Island Series, at a horizon which he places between the Middle and Lower Arenig. 



