6 4 



PEOCEEDIXGS OF THE GEOLOGICAL SOCIETY. 



5 are Trilobita (Asaphus affinis, M'Coy, A. Homfmyi, Salt., Oheirurus 

 Frederici, Salt., Bioni.de atra, Salt., and Ogygia scutatruv, Salt.). It 

 will be observed tbat these are all Tremacloc species, none of the earlier 

 or more pronounced Longmynd, Menevian, and Lingula-flag forms 

 ever appearing above the Lingula-flags ; but assuming that the 

 Tremadoc rocks terminate the lower division of the Cambrian series, 

 they must be acknowledged to be of value. 



The species of Brachiopoda, as we should expect, tell much the 

 same tale. They are Lingulella primceva, L. ferruginea,Y3ii\ ovalis, 

 and Obolella metadata, which do not pass out of the lowest divi- 

 sions ; while Lingula petalon, L. lepis, Lingulella Bavisii, Obolella 

 plicata, and Orthis Carausii, 0. lenticidaris, and 0. menapiai unite 

 the Tremadoc to the Arenig. The remaining species are pelagic 

 Mollusca. jNo G asteropoda occur, and no form of Lamellibranch until 

 we reach the Lower Tremadoc, where 12 species are met with, thus 

 showing this earliest known fauna to have been highly specialized 

 and of long duration ; this would be expected from the great physical 

 development of the rocks, as well as through the large crustacean 

 fauna, which numbers 28 genera and 103 species, only 5 of which 

 passed to the succeeding horizon, or the Arenig, as before stated ; 

 none of the great Olenidse (Paradoocides, Platonia, and Neseuretus) 

 losses to the higher division of the Cambrian or Cambro-Silurian 

 rocks. 



The Pelagic fauna, 5 genera and 18 species, as exemplified by the 

 Pteropoda and Heteropoda, was, and is still, the largest known, in- 

 cluding Cyrtotheca 1 species, Theca 14, Stenotheca 1, Conidaria 1, 

 and Bdlerophon 1. Nine of these are St.-David's forms ; and only 

 2 species of Pteropoda, Theca simplex and Conidaria Homfrayi, 

 with Bellerophon multistriatas, pass to the Arenig ; they will also be 

 noticed under that group. 



Plaxtje. — Granting that the Oldhamiw might be calciphites, or cal- 

 careous corallines, resembling in habit the Melobesice and Nidliporce 

 of modern seas, or the group of corallines so abundant in the seas 

 of warmer latitudes, we are still at a loss as to their true nature, 

 even if organic at all. Goppert refers them to sea-weeds, and com- 

 pares 0. antiqua with the living Liagora ramellosa of Kiitzing 

 from TenerifTe ; but Goppert makes two genera of Oldhamia ; Mur- 

 cliisonites and Oldhamia, the 0. antiqua of Forbes being his Mur- 

 chisonites antiqua. Professor Kinahan and Edward Forbes both 

 referred, them to the class Hydrozoa as having affinities with the 

 Sertulariidae *. The Eev. Mr. Berkeley long ago suggested a resem- 

 blance to the genus Acetabidaria, one of the Chlorospermea) (Chloro- 

 sporese). No traces whatever of these singular remains have been 

 found in any of the Cambrian rocks, either in North or South Wales. 

 Mr. Salter well searched the Cambrian grits near Bangor and Harlech 

 for Oldhamice ; but nothing approaching them was ever detected. 

 Probably their place, in the absence of better evidence, is amongst 

 the Hydrozoa. It is singular that, amidst these grandly developed 



* Vide Baily, 'Figures of Characteristic Brit. Foas.' vol. i. Palaeozoic, p. 1, 

 t. 1 (1875). This book should be in the possession of all students of Palieozoic 

 palaeontology. 



