Lapworth— Graptolites of Co. Down. 
131 
25. Sp. 18. Monograptus gregarius. Lapw. PI. 5, fig. 4 . Locality— The 
characteristic fossil of the central portion of the Birkhill shales. It 
occurs in myriads in the black shales of Coalpit Bay. 
26. Sp. 19. Monograptus argutus. Lapw. PL 5, fig. 5. 
The accompanying figure, as well as that illustrative of the original 
description ot this species, was taken from a cast of a compressed example In 
specimens preserved with their relief the hydrothecse resemble those in 
Dicellograptus, having a deep excavation in the distal portion of their outer 
wall, while the aperture opens obliquely outwards, partly overlapping the 
lateral wall of the common canal. Locality— Coalpit Bay. 
27. Sp. 20. Monograptus Sandersoni. Lapw. PI. c, fig 8 Locality 
Coalpit Bay and Tullygarvan. 
28. Sp. 21. Monograptus tenuis. Portlock. PI. 5 , fig. IO Localities— 
Coalpit Bay and Tullygarvan (?) ’ 
29. Sp. 22. Monograptus attenuates. Hopk. PI. 5, fi g . 3. Locality- 
Coalpit Bay. y 
Genus III. Dimorphograptus, provisional genus. Lapworth. (Geo Ma^ 
1876, p. 545*) 
Examples of this genus are found in great profusion both in Ireland and 
Scotland, and m all we find the characteristic mono-diprionidian polypary. 
Nevertheless, in the complete absence of specimens preserved in relief, I have 
grave doubts of the validity of the genus. We meet with occasional examples 
in which we have a hint of a second series of hydrothecae in the proximal por- 
tion. It is just possible that in this group the concavo- convexity of the poly- 
pary general among the diprionidian Graptolites is carried to excess ; and that 
the partial invisibility of the second series of hydrothecse is due to their lying 
almost parallel with those of the first series. 
30. Sp. 1. Dimorphograptus Swanstoni. Lapw. PI. 6, fig. 5. 
A most remarkable and very distinct little species. It occurs in admirable 
preservation in the Coalpit Bay division of the County Down black shales, but 
has not hitherto been detected in the corresponding zone of the Moffat Series. 
Geinitz figures an example of this species from the Kissel-scheifer of Central 
Germany. (Die Versteinerungen, Taf. 1, fig. 25.) Locality— Coalpit Bay. 
K 
