SUPPLEMENT TO THE MONOGRAPH 



OF THE 



BEITISH FOSSIL TREGONLE. 



The discovery of two species of Trigonia in the Lower Lias of Oviedo, Northern 

 Spain, is an important fact in Palaeontology, as it carries back the genus in Geological 

 time almost to the Trias, and therefore nearly to the position of its allied genus and 

 precursor, Myophoria. Previously, the oldest recorded species of Trigonia of which we 

 have any certain knowledge was the Trigonia Lingonensis, Dum., obtained in the upper 

 portion of the Middle Lias of Prance and England. 1 The Spanish Trigonia now 

 described were obtained by Dr. Charles Barrois, of the Faculte des Sciences, Lille, and 

 are stated by him to occur on the border of the Liassic basin of Oviedo, overlying 

 Trias. I have previously, at page 211 of my 'Monograph on Trigoniae,' mentioned my 

 obligations to Dr. Barrois for his important contributions of Belgian Trigoniae to that 

 work, and have now again to express my thanks and recognition of the high value of his 

 present contribution. Dr. Barrois refers these Trigonia to the Angulatus zone of the 

 Lower Lias, and mentions that he has transferred his Jurassic fossils to his friend, 

 Mons. A. Six, of Lille (Secretary to the Northern Geological Society), who is actively 

 engaged in the study of the Jurassic rocks of Eastern Prance. A subsequent communi- 

 cation obligingly contributed by the latter gentleman, contains much additional informa- 

 tion respecting these Spanish Trigonia, and informs me that the fossils associated with 

 them are in bad preservation, that some of them are new, that there are no Cephalopoda 

 with them, and that he has ascertained the following species of Lamellibranchiata, 

 Cardinia concinna, Sow., Astarte detrita, Goldf., Protocardia Phillipiana, Dunker., 

 Protocardia truncata, Sow., also a gigantic Gervillia, upwards of eleven centimetres in 

 length. These fossils he assigns to the Etage Hettangien or Infra Lias of Turquem and 

 Pictte. The Trigonia were associated with the gigantic Gervillia, the position of which he 

 believes to be the upper portion of the Angulatus zone ; carbonaceous masses also occur. 

 The lithological aspect of the Trigonia resembles that of the fossils generally from the 

 Lower Lias shale ; they are all separated valves. These are the oldest examples of 

 Trigonia of which we have any certain knowledge. 



1 ' British Trigoniae,' p. 98, also pp. 219. 



