i 7 8 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



natus, B. ewpansus, B. Murchisoni, and B. trilobatus ; 6 species 

 occur in the Upper Ludlow of Westmoreland ; Shropshire and 

 Worcestershire possess 3 of the same species. None are known in the 

 Ludlow rocks of North Wales, Herefordshire, Scotland, or Ireland. 

 B. carinatus, B. trilobatus, and B. dilatatus are also Wenlock species. 



Cephalopoda. — No less than 24 species of Orthoceratites, 6 species 

 of Phragmoceras, and 3 of Lituites, with other forms, make up the 6 

 genera and 37 species known in the Ludlow. Ascoceras Barrandii 

 constitutes a new generic type. The Lower Ludlow has yielded 

 4 genera, Lituites (3 species), Orthoceras (15 species), Phragmo- 

 ceras (6 species), and Eocosiphonitcs (2 species). 



The Aymestry Limestone has yielded 3 genera and 6 species — 

 Lituites giganteus, Orthoceras 4 species, and Phragmoceras ventricosum. 

 The Upper Ludlow 5 genera and 22 species — Ascoceras Barrandii, 

 Lituites giganteus, Orthoceras 17 species, Phragmoceras nautileum, 

 and Tretoceras semipartitum. 



In the Passage-beds we have noted Orthoceras bullatum and Tre- 

 toceras semipartitum. 16 species of the genus Orthoceras occur in 

 Westmoreland, mostly Upper Ludlow, and no other genus has yet 

 occurred there. Shropshire possesses 4 genera and 22 species, em- 

 bracing most of the species in the Upper and Lower Ludlow divisions ; 

 Herefordshire 5 genera and 21 species, Ascoceras Barrandii, Lituites 

 3 species, Orthoceras 11, Phragmoceras 3, Exosiphonites2. Worces- 

 tershire has 10 species. Orthoceras Maclareni and 0. subgregarium 

 are the only Scotch forms known ; and 0. subgregarium is the only 

 Irish species. 11 species come from the Wenlock rocks to the Lower 

 Ludlow, but 16 Wenlock species range through the Ludlow group ; 

 Ascoceras is the only new genus ; and none ranged above into either 

 Old Red Sandstone, Devonian, or Carboniferous rocks. 



Pisces. — No Vertebrata have yet been discovered in earlier rocks 

 than the Lower Ludlow. Scaphaspis {Pteraspis) ludensis, Salt., 

 is the first fish known, and the only species in the Lower Ludlow ; 

 none have yet been detected in the Aymestry Limestone, but every 

 known Ludlow form occurs in the Upper Ludlow, and five of them 

 in the Passage- or junction-beds, through which about 20 species of 

 the Silurian fauna pass to the Lower Old Ked Sandstone, 7 of which 

 are Crustacea (Merostomata), 6 Fishes, and 2 Cephalopoda, &c. 



The Crustacea common to the Ludlow and Old Red, and all be- 

 longing to one order, are Eurypterus abbreviatus, E. acuminatus, and 

 E. pygmceus, Pterygotus problematicus, Stylonurus Powriei, JS. me- 

 galops, and Parka decipiens. The fishes that connect the two for- 

 mations, but only in the Silurian area along the frontier of the Old 

 E,ed, are Auchenaspis Salteri, Cephalaspis Murchisoni, O. ornatus, 

 Pteraspis Banksii, Scaphaspis ludensis, and Eukeraspis pustuliferus. 

 All belong to the Ganoidei. 



Devonian. 



Plants. — We have no clue as to the region in which the 

 Devonian Plants first appeared ; and yet small as is the flora of 

 the British Devonian as compared with that of North America it 



