202 BRITISH PALAEOZOIC PHYLLOCARIDA. 



as a new genus of the Dithyrocaridge under the appellation of Lebescontia, after the 

 well-known geologist of Rennes, who discovered it in the Lower Silurian schists of 

 Brittany, and lent the specimens to one of us several years ago for examination and 

 description. Its obscure and complex character suggests .enigmatica for its 

 specific name. The locality and geological horizon indicate that these specimens 

 are the oldest known individuals of this group of Phyllopoda. 



In the Report of the ' Association Francaise pour l'Avancement des Sciences, 

 Congres de Nantes, 1875,' MM. Gaston Le Goarant de Tromelin and Paul 

 Lebesconte gave an account of the Palasozoic Formations of the north-west of 

 France, with lists of the Silurian fossils of the Departments of Maine-et-Loire, 

 Loire-Inferieur, and the Morbihan (' Compte-rendu du Congres,' &c, published 

 in June, 1876, pp. 601—687). 



The palaeozoic rocks of the " massif breton ou armoricain," which constitutes 

 the great peninsula of North-western France, have been studied in more or less 

 detail by mauy geologists, and the memoir mentioned above refers to their work, 

 and gives the result of the special researches by MM. de Tromelin and Lebesconte 

 up to 1875. In 1889 M. Lebesconte kindly lent his collection of the palseozoic 

 fossils of Brittany to one of us, and the phyllopodal specimens here figured and 

 described were noticed among them as being probably allied to Dithyrocaris. 



In the ' Memoir ' by de Tromelin and Lebesconte no particular fossils are 

 recorded from Coesmes, Dep. Ille-et-Vilaine (Brittany) ; but in the Collection 

 above referred to there are obscure remains of Molluscan bivalves, of Trilobites 

 and Eurypterids, also the Dithyrocarid under notice, and one or more specimens 

 of Goleoprion. 



Renaze, whence one of our specimens came, is just south of Brittany, in the 

 ancient province of Anjou, not far from the border of the Departement de Maine- 

 et-Loire, but in the Dep. de la Mayenne. It is in a line with the slate quarries of 

 Riadan 1 and Coesmes (Ille-et-Vilaine). In Table A of MM. de Tromelin and 

 Lebesconte's ' Memoir ' the following fossils are recorded from the slaty schist of 

 Renaze : 



Calymene pulchra, Barrande. 

 Dalmanites socialis, var. proseva, 



Barr. 

 Trinucleus Goldfussi, Barr. 



— ornatus, Sternberg, sp. 



— Pongerardi, Rouault. 



Ampyx tenellus, Barr. 

 Illasnus Beaumonti, Rouault, sp. 

 Acidaspis Buchi, Barr. 

 Serpulites Letellieri, Tromelin. 

 Ctenodonta Cise, Sharpe, sp. 



— Eschwegei, Sharpe, sp. 



1 In the 'Proceedings of the Geologists' Association,' vol. xxi, pt. 3 (July, 1S99), p. Ill, the 

 Eiadau Slates are referred to the Middle Ordovician Series by Dr. C. Barrois ; and at page 132 he 

 refers to ' Bull. Soc. Ge'ol. France,' ser. 3, vol. xiv (1886) ; and ' Annales Soc. Geol. du Nord,' vols, i 

 to xvii, Lille, for literature on the Geology of Central Brittany. 



