1852.] SALTER ON GRAPTOLITES. 391 



This lias been compared with good specimens in the Society's col- 

 lection from Sweden, and no difference can be detected. Mr. Hark- 

 ness has faf oured the Geological Surrey with an excellent suite, of 

 all ages, and, in one or two, spines were observed projecting from the 

 lower edge of the cell, as in Hisinger's species. Prof. M'Coy also 

 quotes G. Sagittarius from this district. 



Description. — Young specimens have the breadth of the notches or 

 cell-mouths greater than that of the shaft ; in middle age the notches 

 are considerably less deep, although the oblique lines of division be- 

 tween the cells extend far inwards and leave but a narrow canal ; in 

 old specimens, which are frequently 1 hue broad and a foot long, the 

 depth of the notches is about one-third of the whole breadth or 

 scarcely so much. The spine in our best-preserved specimens is longer 

 than in those we have seen from Sweden ; but as so few spines are 

 present, we cannot say if this is constant. 



Localities. Glenkihi ; Bran Burn ; Duffkinnell, kc. 



Note. — The species called G, Sagittarius by Portlock (Geol. Rep. 

 pi. 19. f. 8, and pi. 20. f. 1) has very narrow and crowded cells, placed 

 very obhquely, and hardly projecting at all as distinct teeth. I find 

 that Col. Portlock has proposed for it the name of G. Comjbeari in 

 MS. with a description as follows : — " The axial space wide and flat, 

 the serratures closely pressed together, their points appearing very 

 Uttle beyond the axis." 



Mr. Sowerby has used this name in his MS. Catalogues of the 

 Collection of the Geological Society ; and it will, I suppose, be ge- 

 nerally adopted. 



PI. XXI. fio;. 9. 



'©■ 



Of G. laxusf, Nicol (Quart. Joum. Geol. Soc. vol. vi. p. 64), it is' 

 thought desirable to give a figure, in order that a comparison may be 

 made with similarly compressed specimens of G. Sagittarius. 



These admirably show the scalariform appearance produced by the 

 somewhat obhque compression of the canal and cells, as explained in 

 Barrande's treatise on the Graptolites of Bohemia, p. 45-47. And 

 I think that this condition is what has chiefly given rise to Prof. 

 McCoy's idea, that there is at the base of each Graptolite-cell a dia- 

 phragm which nearly closes the base. When the fossil is laterally 

 compressed, the basal edges of the cells, which are placed obhquely 

 by pressure, frequently run in straight Imes as in fig. 9 « ; when the 

 compression has taken place more in the plane of the mouths, a double 

 series of oval marks is the result, as shown in fig. 9 b. 



Locality. Thornielee, Selkirkshire. Collected by Prof. Nicol. 



DiTHYROCARIS? APTYCHOIDES, U. Sp. PI. XXI. fig. 10. 



This remarkable httle fossil is figured rather to call attention to 

 it than to assign it a true position. It is exceedingly hke in form to 

 a pair of the fossils called Aptychus, but there is a slight indentation 

 in each plate, just at the umbo or inner angle (*), which does not 



t See above, p. 388, uote. 



