546 Geological Society : — 



GEOLOGICAL SOCIETY. 



[Continued from p. 481.] 



December 4, 1867.— Robert Etheridge, Esq., F.G.S., 

 in the Chair. 



The following communications were read : — 



1. "On the Graptolites of the Skiddaw Series." By Henry 

 Alleyne Nicholson, D.Sc, M.B., F.G.S. &c. 



The author first described the geological relations and distribu- 

 tion of the Skiddaw Slates, and noticed their correspondence witli 

 the Quebec Group of Canada, and then gave a description of the 

 Graptolites found in these rocks. The genera and their distin- 

 guishing characters are the following : — 



1 . Dichograpsus, Salter (3 species) : possesses a frond repeatedly 

 dichotomous from a basal stipe into 8, 16, or more branches, each 

 with a single row of cells, the lower part of the stipe being enve- 

 loped in a corneous cup. 



2. Tetragrapsus, Slater (3 species) : possesses a frond composed 

 of four simple stipes, arising from a non-celluliferous funicle, which 

 bifurcates at both ends. 



3. Phyllograpsus, Hall (2 species) : differs from the last in pos- 

 sessing a frond composed of four simple stipes united back to back 

 by their solid axes. 



4. Didymograpsus, M'Coy (7 species) : the frond consists of two 

 simple stipes springing from a mucronate radicle, which may be 

 rudimentary or apparently absent. 



5. Diplograpsus, M'Coy (4 species) : two simple stipes, united 

 by their solid axes into a celluliferous frond furnished with a radicle 

 at the base. 



6. Graptolites vel Graptolithus, Linn. (4 species) : simple stipe, 

 with a single row of cells on one side, and a small, generally curved, 

 radicle at the base. 



7. Pleurograpsus, Nicholson (1 species) : celluliferous branches 

 derived from a main celluliferous rhachis. 



2. " On the Fossil Corals (Madreporaria) of the West-Indian 

 Islands. — Part IV. Conclusion." By P. Martin Duncan, M.B., 

 Sec. G.S. 



In this communication the author concluded his series of memoirs 

 on the Fossil Corals of the West Indies with a description of the 

 Miocene corals from St. Croix, Trinidad, and with some supple- 

 mentary remarks on the species described in his former papers from 

 St. Domingo, Jamaica, and Antigua, including notices of new 

 species from those islands. He also gave a complete and revised 

 list of all the fossil corals he had described from the West Indies, 

 including 5 species from Cretaceous strata, 4 species and 1 variety 

 from Eocene deposits, and 102 species and 26 varieties from the 

 Miocene formation, making a total of 111 species and 27 varieties. 

 Of the Miocene species 11 still exist, namely, 6 in the Caribbean 



