ANNIVEESAEY ADDEESS OP TELE PEESIEENT. 



215 



species ; and 7 of the 8 horizons possess them : 9 genera and 18 

 species occur in the Calciferous Sandstones of Scotland; 11 genera 

 and 80 species range through the thin-bedded Carboniferous Lime- 

 stone Shales, or the Lower Limestones ; 14 genera and 172 species 

 have been collected and named from the Carboniferous Limestone 

 alone ; 10 genera and 31 species are from the Yoredale rocks and 

 Upper Limestone Shales; 11 genera and 24 species are Millstone 

 Grit ; the Lower Coal-measures yield 9 genera and 18 species, and 

 the Middle 3 genera and 3 species. "We know of no Brachiopoda in 

 the Upper Coal-measures. The whole group, with every species, has 

 been exhaustively worked out by T. Davidson, Esq., F.R.S., in the 

 volumes of the Palaeontographical Society ; nothing is left undone 

 by that distinguished brachiopodist, whose labours in this field of 

 palaeontology are universal. To Mr. Davidson we are indebted for 

 the highest research into the morphology, history, and classification 

 of this most difficult class of Mollusca. 















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The preponderance of the two genera Pro ductus and Spirifera is 

 a great feature in the Carboniferous rocks. Chonetes, Bhynckonella, 

 and Orthis follow in importance so far as the number of species lends 

 significance. Chonetes and Productus make their first appearance in 

 these rocks, and, with Retzia, Streptorhynchus, and Cyrtina, dis- 

 appear at the close of the period. 5 genera and 6 species of Bra- 

 chiopoda pass to the Permian; they are Oamarophoria globidina, 

 Phill., G. Schlotheimi, V. Buch, Biscina Koninckii, Geinitz, Lingula 

 Credneri, Geinitz, Sjpirifera Clannyana, King, and Spiriferina cris- 

 tata ; and beyond 2 species of Ostracoda I know no other connecting 

 or transgressive species than the above ; in other words, only 8 

 species of all orders pass to higher rocks out of the Carboniferous 



