WORK OF PORTUGUESE GEOLOGICAL SURVEY. 441 



these trilobites appear to belong to the characteristic Cam- 

 brian families Olcnidcs and Conoccphalidce. Delgado, indeed, 

 compares them with the genera Liostracus and Lcptoplas- 

 ttis ; but unfortunately no figures have yet been published, 

 and all that the descriptions enable us to say is that they 

 probably belong to the Olenus group. This discovery is of 

 oreat interest, for at one time it was believed that the 

 Olenus fauna was absent in Southern Europe. Recently, 

 however, it has been found also in Sardinia. 



The Ordovician and Silurian rocks are much better de- 

 veloped than the Cambrian, or at least they have been far 

 longer known and have yielded fossils much more abun- 

 dantly. One of the best known localities is that of Val- 

 longo, 10 km. E.N.E. of Oporto, where Sharpe obtained 

 a number of Ordovician fossils which were described by 

 himself and others (41). Recently, Delgado has published 

 a new list of the forms from this neighbourhood, and he re- 

 cognises three distinct horizons (19). But there is some 

 confusion in the identification either of the horizons or of 

 the fossils ; for from the third horizon he records, for 

 example, both the Lower Ordovician form Acidaspis Buchi 

 and the Silurian species, Phacops Doivningice. Most of the 

 Vallongo specimens are certainly Ordovician, and among 

 them are Placoparia, Calymene, Tristani and others, charac- 

 teristic of the Anoers slates of France. 



At Bussaco, some 20 km. north of Coimbra, Silurian 

 fossils, as well as Ordovician, are found in some abundance. 

 The Ordovician beds consist of a lower division of quart- 

 zites, sandstones, black shales and limestones, with Caly- 

 mene Tristani, Placoparia Zippci, etc. ; and these are suc- 

 ceeded by ochreous argillaceous rocks with Phacops Dujar- 

 diui, etc. The Silurian is represented by blue shales and 

 argillaceous schists with graptolites, Cardiola interrupts and 

 the thin-shelled Orthoceratites which Forbes called Creseis 

 (38). Such forms are characteristic of our Lower Ludlow, 

 and to a certain extent of our Wenlock beds. 



South of the Tagus, in the neighbourhood of the grani- 

 tic mass of Portalegre, Delgado has reported the presence 

 of Ordovician beds (15). They commence with a series of 



