ANNIVERSARY ADDRESS OF THE PRESIDENT. CVll 



attached to the distinction of certain genera, he admits the necessity 

 of forming generic divisions, founded on an assemblage of well-observed 

 characters, often taken from internal structure, in order to classify 

 the multitude of species presented by nature. 



Mr. Da^ddson refers to the new classification of brachiopods by M. 

 d'Orbigny*, and to an examination of his Silurian brachiopods ^ith 

 him. Mr. Da^ddson provisionally arranges the brachiopods of the 

 Upper Silurian series and^described by him under the genera Produc- 

 tus, Chonetes, LeptcBna, Orthis, Spirife7\ Terebratula, PentmneruSj 

 Lingula, Crania, and Orbicula. He notices 78 species, and figures 

 48 of them, and a table is given of the 78 species, the names being 

 those adopted by M. de Verneuil and himself. The synonyms are 

 appended, and reference, in connexion with them, is made to the 

 genera adopted by M. d'Orbigny. The particular stages of the Si- 

 lurian system and the localities are mentioned, and other places where 

 the species are found, either in Europe or America, are added. 



M. de Verneuil communicated a note on some brachiopods of the 

 Isle of Gothland, in which he refers to the labours of Mr. Davidson 

 on the brachiopods of England and to the work of M. Barrande on 

 those of Bohemia, and describes, with figures, seven new species of 

 brachiopods under the names of Leptcena Loveni, L. enigma, Orthis 

 Davidsoni, O. punctata, Spiinfer Marklini, Sp. Barrandi, and Tere- 

 bratula bicarinata, adding the Orthis biloba of Linnaeus. A list is 

 given of the brachiopods of the Upper Silurian system of the Isle of 

 Gothland. In this are enumerated seventeen species of Terebratula, 

 two of Pentamerus, eleven of Spirifer, nine of Orthis, nine of Lep- 

 tcena, and one of Chonetes. 



M. de Verneuil also read a note on certain species of Leptcena, 

 having a perforated beak, noticing Leptcena alternata (Conrad, De 

 Verneuil and Keyserling), L. planoconvexa (Hall), L. sulcata (De 

 Vern.), L. Loveni (De Vern.), L. antiquata and scabrosa (Davidson), 

 L. analoga and depressa (on the authority of Dr. King and Mr. Da- 

 vidson), X. tenuistriata (Sowerby), and L. planumbona (Hall). 



M. Fauverge communicated observations on the opinion of Dr. Boue 

 respecting the coincidence of the isothermal lines of previous geologi- 

 cal times with the present, remarking, as regards the coal-measures, 

 on identical species of the plants found fossil in them being discovered 

 imder very different latitudes, and referring to central heat as the 

 cause, at that period, of the surface-temperature of the globe. We 

 may remark on this subject (one on which we have elsewhere entered), 

 that as exact geological investigations progress, with reference to the 

 varied distribution of land and water, and all the conditions of relief 

 of the land and form of the sea-bottom, we may anticipate very im- 

 portant information as to the distribution of temperature over our 

 planet's surface at different geological times. A better insight will 

 also be obtained into the value which has to be attributed to the in- 

 ternal heat of the earth, up to the period when, from the loss of heat 

 by radiation into planetary space having been sufficiently advanced, 



* Comptes Rendus de rAcademie des Sciences, torn. xxv. 



