Lapworth— Graptolites of the Co. Down. 133 
40. Sp. 8. Diplograptus Hughesi. Nich. PI. 6, fig. 14. Locality— Coalpit 
Bay. 
41. Sp. 9. Diplograptus insutiformis. Nich. PI. 6, fig. 15. Locality — 
Ballygrot. 
42. Sp. 10. Diplograptus folium. His. PI. 6, fig. 16. Locality — Coalpit 
Bay. 
43. Sp. 11. Diplograptus truncatus. Lapw. PI. 6, fig. 17, 
Diplograptus pristis, var. truncatus. Lapw. (Catl. Western 
Scott, Fossils. Plate 1, fig. 28.) 
Polypary diprionidian, sub-fusiform or with parallel margins, one to three 
inches in length and one-eighth of an inch in maximum diameter; fur- 
nished proximally with a minute radicle and lateral spines. Virgula 
invisible. Hydrothecse inclined at an angle of about 45 degrees, 
linear-tubular, expanding towards the oblique apertural margin and 
ornamented with minute transverse strise. 
There are several varieties of this species in the South Scottish rocks, but 
they agree generally in the foregoing characteristics. Some smaller and wider 
examples of this form are almost inseparable from Dip. palmem. Forms pre- 
served in relief show no trace of a longitudinal septum on one of the lateral 
faces. I formerly referred this species to Diplograptus pristis of Hisinger, but 
Swedish specimens of the latter show a polypary and hydrothecse of the general 
type of Diplograptus quadrimucronatus (Hall). 
44. Sp. 12. Diplograptus foliactus. Murch. PL 6, fig. 18. Locality — 
Ballygrot. 
45. Sp 13. Diplograptus vesiculosus . Nich. PI. 6, fig. 19. Locality — 
Coalpit Bay. 
46. Sp. 14. Diplograptus quadrimucronatus. Hall. PL 6, fig. 20. 
In the Scottish examples referred to this species, four rigid spurs are usually 
given off, one from each of the angles of the prismoid polypary at a normally 
uniform height corresponding to the position of the sixth or seventh hydrotheca, 
counting from the initial extremity. 
In the Irish forms collected by Mr. Swanston the spurs are sometimes 
