Swanston— Silurian Rocks of Co. Down. 
113 
up into the prevailing purple and grey slates of the district. Graptolites have 
been found in the less altered portions of the black shales, they are, however, 
very indistinct, and onlv two species — Leptograptus flaccidus, Hall, and Dip- 
lograptus truncatus , Lapw.=#m/A, His. — could with certainty be made out. In 
a thin pale grey arenaceous band associated with them occur plant remains, 
which have been identified as belonging to the genus Buthotrephis , but appar- 
ently of a species not hitherto figured. 
Carnalea. — On the shore north of Carnalea Railway Station (Belfast, 
Holywood and Bangor Railway) just where a small stream flows into the Lough, 
there is a small exposure of black shales almost vertical. To the south-east 
they abut against grey slates and grits, and seaward they are covered with 
shingle and sand. These black shales are rich in fossils, but from the shivery 
nature of the beds they are usually in a fragmentary state. Among the most 
characteristic are the following : — 
Diplograptus truncatus, Lapw. Dicellograptus Forchammeri, 
„ quadrimucronatus, Hall. Geinitz. 
Lasiograptus Harknessi, Nick. „ elegans, Carr. 
Retiolites fibratus, Lapw. Leptograptus flaccidus, Hall. 
Climacograptus tubuliferus, Lapnv. 
Crawfordsburn. — Immediately opposite Crawfordsburn House, on the 
shore near low water mark, grey mudstones and black shales occur, the general 
strike of which is N. 20 E. In one place, however, the beds are broken 
sharply across, bent in a direction exactly at right angles to it, and in part 
inverted. Fossils are few and fragmentary. 
Ballygrot. — This locality, named from the townland in which it occurs, 
is near Grey Point, and is also situated on the shore. The rocks consist of a 
series of pale green mudstones and black shales, which are again followed by 
a band of grit and an exposure of several hundred feet of black ferruginous 
shales, containing flinty bands, and which are much threaded with quartz. 
Faulted against these to the north is a series of purple and grey shales, which 
are again followed by black shales similar in character to last. Irregularly 
bedded grits and slates succeed these, and prevail for a considerable distance. 
No fossils have been detected in the grey or purple shales, but the less altered 
