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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



Fig. 2 b. The same ; caudal shield. Mulloch Quarry. 

 Fig. 3. Illcenus, sp. {III. BowmanniT). Mulloch Quarry. 

 Fig. 4. Encrinurus punctatus, Briin. sp. 

 Fig. 5. Lichas laxatus, M'Coy. 



Fig. 6 a. Tentaculites ornatus, Sow. var. ; natural size. 

 Fig. 6 b. The same ; magnified. 



Fig. 7. Petraia subduplicata, M'Coy. Mulloch Quarry. 



Fig. 8. Variety of the same, with more equal lamellae. Mulloch Quarry. 



Fig. 9. Heliolites subrotundus, Fougt, sp. {Porites piriformis, Lonsd. Sil. Syst.) ; 



a cast of the tubes of the upper surface : they stand out in relief, and 



are slightly indented by the twelve small lamellae. 

 Figs. 10 a, 10 b. Hemithyris angustifrons, M'Coy ; interior cast of both valves. 

 Figs. 11a, 11 b. Terebratula cuneata, Dalm. ; two specimens. Lower Thrave. 

 Fig. 12 a. Atrypa hemisphcerica, Sow. var. (Hemithyris Scotica, M'Coy) ; dorsal 

 valve. 



Fig. 12 5. The same; ventral valve. 



Fig. 12 c. The same ; interior cast of dorsal valve. 



Fig. 13a. Orthis reversa, Salter; interior cast of dorsal valve. 



Fig. 13 b. The same; interior cast of ventral valve. 



Fig. 13 c. The same ; exterior surface of dorsal valve. 



Fig. 14. Trochus Moorei, M'Coy? Mulloch Quarry. 



Fig. 15. Turbo, sp. ; probably new. Mulloch Quarry. 



Fig. 16. Nidulites favus, Salter; cast of the lower side of one series of cups. 



Fig. 17 a. The same ; interior cast of one series of cups. Mulloch Quarry. 



Fig. 17 6. The same ; side view of complete plate, showing both series. 



Fig. 18a. Bellerophon acutus, Sow.; side view. 



Fig. 18 6. The same ; edge view. 



Fig. 19. Orthoceras Barrandei, Salter. Mulloch Quarry. (N.B. The septa are 

 too indistinctly marked in the figure.) 



PLATE X. 



Fig. 1 a. Graptolithus tenuis, Portl. ; natural size. Piedmont Glen. 

 Fig. 1 b. The same ; magnified. 



Fig. 2a. Diplograpsus bullatus, Salter; natural size. Ardwell. 



Fig. 2 b. The same ; magnified, and viewed a little obliquely to show the thickness. 



Figs. 3, 4. Orbicula ? crassa, Hall. Penwhapple. 



Fig. 5. Orthoceras politum, M'Coy ; reduced one half. 



Fig. 6 a. The same ; showing the distance between the septa. 



Fig. 6 b. The same ; showing a septum and the siphuncle. 



Fig. 7. Orthoceras vaginatum, Schloth. ? 



Fig. 8. Cyrtoceras, sp. 



February 26, 1851. 



The following communication was read : — 



On the Silurian Rocks of the South of Scotland. Part II. 

 By Sir Roderick Impey Murchison, G.C.St.S., F.R.S. G.S. 

 L.S., Hon. Mem. R.S. Edinburgh, R.I. Ac, Mem. Imp. Ac. Sc. 

 St. Petersburgh, Corr. Mem. Ac. France, Berlin, Turin, Copen- 

 hagen, &c. &c, and President of the Royal Geographical Society, 

 London. 



[Abstract printed with Part I. p. 168, above.] 



