﻿1850.] HARKNESS ON THE GRAPTOLITES OF DUMFRIESSHIRE. 61 



size appear to show that there is a gradual tapering towards the apex, 

 the younger portion of the individual having the cellules of smaller 

 size than the adult part. In the adult portion some traces may be 

 detected on the dorsal margin of a fine axis, and the interval between 

 this and the cells is about one half of the breadth of the latter. The 

 cells are directed outwards, having a slight inclination upwards. 

 They are adherent to each other only at their base, and as they pro- 

 ceed outwards their ends are distinct, a considerable space occur- 

 ring between them. The cells narrow upwards, and then suddenly 

 swell toward their termination into a rounded and curved knob, on the 

 lower side of which is the mouth. No appendage is found at the 

 extremity of the cells. In an individual exceeding a line in breadth, 

 the number of cells was about twelve in an inch ; in others of the 

 same breadth this number was exceeded, and sometimes fewer oc- 

 curred, the space separating them being of various breadths. 



All the specimens of this graptolite were converted into iron py- 

 rites, and the state of preservation is imperfect, the most common 

 appearance being that of a white impression, the result of the decom- 

 position of the sulphate of iron. The locality which affords it in 

 greatest abundance is the Bell Craig Burn near Moffat. 



3. Graptolites Nicoli, Harkness. 

 Pl. I. fig. 6. Natural size and magnified. 



This species, which I have met with only in a fragmentary state, 

 appears from its breadth to be of considerable size, and to have a 

 straight form. The portions which I have obtained partake of the 

 characters of the preceding species, from which it is distinguished 

 only by the cells passing directly outwards, and having no inclina- 

 tion to the common canal, but being at right angles thereto. It 

 wants also the pedunculated form of cell which marks Grapt. Bec/ci, 

 these being nearly of regular thickness from the base to near their 

 rounded extremity. It is usually converted into iron pyrites, and 

 imperfectly preserved, and occurs, in company with the preceding one, 

 at the Bell Craig Burn ; also at Glenkiln Burn, about seven miles 

 north of Dumfries. 



It is probable that the difference in the form and position of the 

 cells above described are not sufficient to establish a specific distinc- 

 tion between this and the G. Bec/ci, but it is thought worth while 

 to figure it, as at least a remarkable variation. 



4. Graptolites Nilssoni, Barr. 

 Pl. I. fig. 7. Natural size and magnified. 



(Barrande, loc. cit. pl. 2. figs. 16, 17.) 



In this species the polypidom is very thin, sometimes straight, and 

 sometimes slightly curved. The specimens in my possession do not 

 show the young portion. In some individuals traces of an axis are 

 seen along the dorsal margin, and the space between this and the 

 base of the cell is of greater breadth than the cellules themselves ; 



