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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 4, 



tion shows some difference from the adult. At the apex the cellules 

 are smaller and have a partially recurved form. In the adult portion 

 they are directed outwards, and the axis seems to be broader than is 

 common in this genus. This, however, is caused by the base of the 

 cells being enlarged and brought near together. They grow rapidly 

 narrower from the base to the opposite extremity, and have thus a 

 triangular form, whence the specific name. A depression runs along 

 each cell similar to that occurring in the preceding species. 



In the adult portion the number of cells in two lines is five. Our 

 specimens present a shining pyritous surface, and no trace of the 

 external covering is manifest. This form is common in the shale of 

 the Frenchland Bum near Moffat, and also at Bell Craig Linns. 



Graptolites, Linnaeus, Beck, &c. 



1. Grapt. Sedgwickii, Portl. 

 Pl. I. fig. 4. Natural size and magnified. 



(Portlock, Geol. Report, pl. 19. figs. 1, 2, 3, 6.) 



Polypidom straight and of considerable length ; the apex appearing 

 to attenuate rapidly. The young portion seems to present no dif- 

 ference from the adult, except in having the cellules of smaller size. 

 In well-preserved specimens a linear axis is seen running along the 

 margin of the polypidom. The canal is about as broad as the teeth, 

 which at their extremity are rounded, and turn slightly downwards. 

 The mouths of the cellules are remote from each other, and from the 

 lower part of them a long spine emanates. In an individual exceed- 

 ing the twelfth of an inch in breadth, the number of cellules in an 

 inch is twenty. 



When in a good state of preservation, this fossil consists of carbo- 

 naceous matter having a shining appearance and smooth surface ; it 

 is met with in great abundance in the course of the Duff Kinnell, a 

 small rivulet near Rae Hills, about twelve miles from Dumfries. 



This is figured afresh, to show the long spine projecting from the 

 tip of the cell. The form of the cells is not well shown in Port- 

 lock's figure. The original specimens have been compared with mine. 



The possession of a spine gives this graptolite somewhat of the 

 character of the G. colonus and G. Halli of Barrande. The length 

 of the spine is greater than in either of these two. 



2. Graptolites Becki, Barr. 



Pl. I. fig. 5. Natural size and magnified. 

 (Barrande, loc. cit. pl. 3. fig. 14 to 18.) 



G. lobiferus, M c Coy, Ann. & Mag. Nat. Hist. vol. vi. 270 ; Cat. 

 "Woodwardian Museum, pl. IB. fig. 3. 



This graptolite is generally of great size ; in one instance a speci- 

 men was traced which exceeded 1 8 inches in length, although neither 

 the base nor the apex was discovered. The individuals which I have 

 hitherto met with are straight, and some portions which are of smaller 



